Was writing material for to-do list accessible in medieval Europe?

Short answer: yes there was writting material to write a to-do list in Medieval Europe.

There were plenty materials:

• Parchment: using any erasable tool, carbon stick, chalk, but mainly, water dissolvable inks. This was not that expensive and very reusable.

• Paper: paper was first used in Europe in medieval times, since 8th century in Spain (Muslim conquest). So, nearly all of medieval Spain had paper available, the same for Italy (this is not true in northern Europe).

• Most non-glossy ceramic surfaces are writable (ostrakon).

• Also consider wall surfaces, polished stone or whitened walls (calcium oxide), very writable.

Without necessarily disputing either @MCW or @Samuel Russell's answers, aren't we somewhat missing a key point? Most people were illiterate, therefore a to-do list was simply not on the radar.

For those that were literate, I'd say the OP is talking about using paper for "short and ephemeral note taking or calculations of any kind" not just an agenda of actions for the day (a "to-do list").

From my own experience in the late medieval period (1300-1500), I'd agree with MCW that that certainly exists and can be found relatively readily. While I take Samuel Russel's point that people viewed the world very differently, all I can say is that in their informal scribbles they usually look like regular folk to me. Jokes, doodles, comments and often a clear attempt to show the importance of the individual ("this book belongs to ...", "written by ...") are not hard to find.

So did they take notes on scraps of paper? Yes. Was paper still too scarce to make a habit of it? Yes. Were other devices such as tally sticks used for numeric calculations and accounts? Yes, and they were also used on a more formal basis to record things like debts via "split tallies". The original House of Parliament in London were destroyed when 600 years-worth of tally sticks were ordered to be burned, and the blaze got out of control.

Paper and vellum were used and re-used, so there are lots of books bound with pages ripped from other books or documents viewed as no longer important.

Finally, the OP seems to discount wax tablets as something that could be used for a note that needed to last more than an extremely short amount of time (hours?). I'm not sure that's correct. At the hospital at Enns wax tablets were used to keep track of amounts payable, erasing and updating amounts as money was received. Isn't that's exactly the sort of aide-mémoire that the OP was interested in? Wax tablets were still being used in Germany in the late 19th century.

On a side note, I'm not even sure that the modern "to-do" list has a very long history in our own age. I don't recall my parents in the 1970s having a lot of paper products around for things that would get written on and then discarded maybe within hours. That's anecdotal, I know, but the main place for things that needed to be remembered was a calendar in the kitchen or the family address book.

As recently as the last 30 years there were people who would tie a knot in a handkerchief if there was a thing they needed to remember to do. My grandmother did it, and I think I did once or twice. Until I was in my 30s, when computers and sticky notes became universal, I'd have written any short term note on the back of my hand or in a pocket diary (ie pocket planner or date book to North Americans). We can't underestimate how much simpler life was within living memory for the vast majority of people (and how much less prone to using resources that cost money), let alone 700 years ago.

As a book historian - albeit of a much later period, I would tend to turn to the Cambridge History of the Book for questions like this, and my answer is largely taken from that, as well as from knowledge I have from spending a lot of time working on the history of paper.

At least in England, after 1300 someone with some level of disposable income could get paper. Paper was made from recycled rags, which were produced from old clothes. Most paper was made from linen, which was produced in France and the Netherlands, and then exported. Its hard to say how much a sheet of paper cost, but paper came in a variety of qualities, and wastepaper was unsurprisingly the cheapest. I am not a medievalist, but I have worked with medieval manuscript, and ephemeral writing of some description is present in lots of miscellaneous manuscripts. I haven't encountered a to do list, but paper was definitely accessible - at least to those who could afford to access writing materials.

Before 1300, lacking accessible and widespread paper, it's somewhat trickier. Parchment is expensive, given you need animals to get hides from to make it. That means you need land, specialists who can produce it and then an excess to sell on. This could be hard to get given you had scriptoria and legal documents to make out of parchment. I've not encountered a parchment to do list but it's not totally unbelievable that someone working with the stuff could've done something like this.

I think the tldr is it is difficult to generalise - there is not a h*m*genous 'medieval world' so prices and availability of materials will be different. However, given the fairly huge amount of ephemeral writing in English, I would be very surprised if people weren't doing the same elsewhere.

It's not a to-do list, but you might just about call it note-taking...

Medieval stone masons were known to use 'tracing floors' to make temporary architectural and design drawings.

Laid with several thin layers of plaster of Paris, the floor was a convenient space for the master mason to draw designs for elements and moldings to scale. There is evidence to suggest that a new layer of plaster would be laid at regular intervals and trampled flat to provide a fresh working surface, with the plans copied onto thin timber or metal sheets for templates. Drawings could easily be brushed out or partially erased, with the most recent etchings shown in the sharpest, clearest white.

Medieval Masons and Tracing Floors - drawingmatter.org

In the UK, surviving tracing floors can apparently be found at York Minster and Wells Cathedral.

The concept of a pre-modern individual is pretty dodgy. The standard medieval minimal economic unit varied from the household to the village. As shown in admittedly high medieval Christine de Pizan's works the aristocratic or noble household counter modeled on the idea of the peasant household as economic unit. Individuals with "to-do" lists did not exist. People were enmeshed in complex social structures at the lowest level where they had assigned places, purposes and functions. This is shown in the long rent periods, the long apprenticeship periods, and the long periods between tenure enforcement in complex ('walked boundary') tenures. People as economic individuals did not exist: individuals didn't have to-do lists. "I" am not the centre of economic activity, "the house X that as my father is X, and as his son I am of the house X;" "the community of Christ of the rule of X of the grant of Y of which I am a member as a ordained / novice / lay." (Annales on French village economics is useful.)

• Group work. Collective social activity reduces the need for individual performances and externalises work-process memory: you don't have to remember it is the time to sow seed when it is the time of sowing seed.
• Tradition. Memory is unnecessary when the memorisable is written into social performance and terrain.
• External social order ("sub-ordination"). When you have no effective choice on gross performances, the memorialisation of them is unnecessary.
• Internal social order. Someone lower in the family, clan or village can be ordinated to perform for you.

For individuals:

• Memory (rhyme, poetics). Cast your eye over the landscape and the boundary markers and memory games pull out the property agreed for leasehold without copy immanently.
• Cut sticks for counting. Well attested regularly found.
• Knocks, knicks, marks, dust.
• For the scholar or later kleine burger: chalk, charcoal, boards and walls

Bibliography

• Ariès, Philippe et al. eds, A History of Private Life (5 vols. 1987–94)
• Bloch, Marc. Feudal Society: Vol 1: The Growth and Ties of Dependence (1989); Feudal Society: Vol 2: Social Classes and Political Organisation(1989)
• Chartier, Roger. Inscription and Erasure: Literature and Written Culture from the Eleventh to the Eighteenth Century (2007)
• Gurevich, Aaron J., and Ann Shukman. “Oral and Written Culture of the Middle Ages: Two ‘Peasant Visions’ of the Late Twelfth-Early Thirteenth Centuries.” New Literary History 16, no. 1 (1984): 51–66. https://doi.org/10.2307/468775.