As far as I can see and from response back from Tech support GMAIL is no longer supported by Outlook...it sort of occasionally works but
You cant move emails to folders without them being duplicated, if you try and delete the dummy duplicate this can ( and its 50/50 ) delete thee actual email and the copy
Outlook does not sync with online GMAIL so folders in GMAIl no longer have same emails in them as in Outlook
You can not add edit or delete folders
You can not use categories
etc etc - responses from support:
If the account is added as Google Cloud Cache, Categories are not yet supported at this time here in Outlook for Mac.
<But Outlook does not give you an option.>
..
"As we still do not have an ETA for the fix at the moment, may I archive this ticket "
So rant over. It's broken.