Upvote:2
There is no need to apply separately for a grace period, as if you have filed for renewal before expiry you automatically get a 6 month grace period (which is currently a 12 month grace period due to processing and Covid-19 delays).
From the CBP Help Q&A I have submitted my Trusted Traveler application for review. Did CBP receive my application?:
If you submitted a renewal application before expiration of your current membership, then you can continue to use your benefits until the renewal is finalized (up to 6 months after your expiration date).
See also this answer to Entry to the US with an expired Nexus
Additionally I have found a number of reports that the grace period for Global Entry has been extended out to 18 months, however I haven't found anything official or that says this also extends to NEXUS or SENTRI. See 18 Month Global Entry Renewal Grace Period