After upgrading to Splunk Enterprise 8.1, I seems to be encountering same issue with
https://community.splunk.com/t5/All-Apps-and-Add-ons/Lookup-Editor-Won-t-save-edits-after-update-to-...
Yet adding 'upload_lookup_files' did resolve my issue. Would anyone happens to know capabilities needed for upload/edit/delete the tables?