From @philsward in https://github.com/backdrop/backdrop-issues/issues/4829#issuecomment-781...
Also, both Themes and Modules need a "remove/delete" option to completely delete them from the file system. Once a theme or module is installed through the GUI, there is no way to get rid of it from the GUI.
GitHub Issue #:
5320
Recent comments
This is good enough, but maybe the module maintainer would like to add such a feature.
specific webform permissions
This should be allowed atleast on private files directory. Accepted your answer though.
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