Originally Posted by ExtremeDude2
You cant use old savestates in 2.3, you really shouldn't be using them at all over normal saves anyway.
You can in current Git version. Both compressed and uncompressed saves work now, old and new savestates. If a new savestate doesn't exist, it will look for an old one. After loading an old savestate, saving again will save it using new savestate, old savestate is not deleted.
It might be better to have an advanced option to use old or new savestates instead.