Any time Krita doesn't have any documents open the interface is locked. There's no way to pick colours, manage your brush presets, brush collections, palettes etc. without having something open. If someone wants to customise their resources they have to create a blank document so that the interface becomes unlocked. If they close all documents, the interface becomes locked again. Reproducible: Always Expected Results: Please make the interface always unlocked. It's reasonable to be able to edit a brush preset and your brush collections\tags, bundles etc. even if you don't have images open.
Sorry, while I agree that it would be nice, it just is not possible in a reliable way.