[...] the manual cost basis for unlisted tokens is not saved between backups or exports [...]
I only notice this on exports, but not on backups.
I.e. when I enter a custom cost basis (be it for listed or unlisted coins) and making a backup, then restoring from that backup also restores the cost basis.
I have a few transactions with custom values myself, so I made sure the backups restore those values.
But just to be safe I rechecked just now to confirm:
- Added a trade to buy 23 YYY (unlisted coin) for 42 USD
- Entered a custom YYY buy value of 8.15 USD
- Saved a backup
- Deleted all trades
- Restored from backup
-> Custom value of 8.15 USD was still set.