score:2
Yes, it's possible. Source: UKVI email followed up with personal experience.
If the application is granted and the applicant already has entry clearance beyond the start date of their new visa, they should be told that the extant leave will be cancelled and no refund issued.
The entry clearance should be crossed out by writing βRecommend cancel without prejudiceβ diagonally across the redundant visa (in red ink), make a note in Proviso and then grant fresh entry clearance in the same passport as the previous leave.
https://www.gov.uk/government/publications/extant-leave-ecb22/extant-leave-ecb22
In my case, the new visa was in a new passport and no note was made across the old one.