Is your feature request related to a problem? UTXO locks are stored in memory only. Nodes start with zero locked outputs, and the locked output list is always cleared (by virtue of process exit) when a node stops or fails. It was added as memory-only filter in https://github.com/bitcoin/bitcoin/pull/1861/
Few users wanted persistency for locking unspent in issue: #14907 but it was closed in May 2020 because of lack of interest.
Describe the solution you’d like: Use wallet db for locked UTXOs
Describe alternatives you’ve considered: Use other wallets
Additional context: I tried fixing this, initially had issues related to wrong use of vector in C++ and could never resolve it after trying few things.
I think it will be easy for devs who work on wallet related issues in Bitcoin Core or anyone else good with C++. Would appreciate if someone could fix this and improve privacy in Core wallet.