Bonus points for some open standard, but some kind of understandable format even if proprietary is miles ahead of proprietary and cryptic.
I wish Fusion360 for example had a sanely git-able on-disk format like:
line 0xdeadbeef (0,0) - (123,456)
line 0x01234567
constraint parallel 0xdeadbeef 0x01234567
Etc., Or something.(Actually I suppose git - and incremental backups - is the main reason I say I'd still prefer plaintext to db.)