By using a mending book (I'm using the mending nerf option) you can force every application of a new enchantment to cost 1 level, this also applies to renaming the tool while applying the enchantment(s).

Eg. when combining any number of books, so long as you include the mending enchantment in the combining process the cost will always be 1 level per anvil use (although the mending book is consumed, it still allows you to reduce the XP requirement to be neglidgable, which seems like it would be unintended?)

AutoRegLib-1.6-49
Quark-r2.4-316
Forge-36.2.0

Hello! Quark's moved to 1.18 now-- unfortunately, this means that (unless your bug is critical and/or game-breaking), we're closing support for issues filed for versions prior to it (e.g. Quark on 1.16).

If your issue still occurs on 1.18, or if your issue happens to be rather critical (e.g. consistently crashing the game with no other mods present), please leave another note or open a new issue. Thanks for your cooperation!