One can disable "Show action to permanently delete files and folders" to hide the delete item. However, it will still show up in the context menu of sidebar items. I don't think this is intended.
Thanks for reporting! True, this is not intended. The bug should be fixed together with Bug #14410 *** This bug has been marked as a duplicate of bug 14410 ***
Fixed now. Make toggle for the delete entry affect side pane too https://git.xfce.org/xfce/thunar/commit/?id=09e39975056ad8d0227ca688704624379b334cd3
Thanks!