I worked on this problem and came up with a solution that is simple to implement. This will work until PGC can implement your request. The steps:
1. Create a List on geocaching.com called Did Not Find (DNF)
2. Add all your DNFs to that list
3. PGC - Tools / Mapbookmarklist
See my implementation in this link https://project-gc.com/Tools/MapBookmarklist?profile_name=TigreToot&owner_name=TigreToot&bmcode=BM89GC3
Of course, there is a bit of manual management involved meaning you will have to delete newly found or add newly DNF caches. Good luck and I hope this helps.