i've had this bug for a while now, past versions of 4.30 included if i remember correctly. i'm using the prealpha 4.30 git 818c841 atm. whenever i edit one of my custom brushes and overwrite the preset, - the brush duplicates (creates a backup), - disappears from my custom tag (still visible under all brushes) - and remains unassignable until i restart krita (says it still has the tag when i press rmb on it in the brush presets selector, but isn't visible in my radial menu or when i select the custom tag in the brush presets). i'm using windows 10
That's a part of resource rewrite.
ah okay, thanks for letting me know!
*** This bug has been marked as a duplicate of bug 392998 ***