Is there a way to add multiple values for User permission, or to set the prohibited value instead of all allowed values (a long list in many cases)
Permissions are all explicit in ERPNext, so there’s no way to define prohibitions. If you’re looking to speed up the process, you could do a data import into the Custom DocPerm doctype.
In terms of usability this is a big disadvantage. Assuming a grocery store that want to limit access to one items category then he will have to add permission for all users for each new category just because he wanted one exclusive category
The other solution is to customize the doctype and add a Flag, however, we will end up with a large number of flags
If you want more complex permissions structures, especially those with complex conditionals, your best bet is probably a permission query: