I use DevonThink to read many RSS feeds, and when a particular post/article is of interest for future reference, I simply move it to a specific group. Most of the time, I just delete the article, as it is not of any value for my work.
The problem is that I end up with a lot of Tags that get imported from the RSS feed articles. Once I delete the article, the tag remain but is unused. The list of tags become so long with most of the entries unused that it becomes unusable.
Is there any ways to prevent the tags from being imported from the RSS feed? Or if not, then how can I delete the unused tags massively?
You can create a smart group, kind is group, and sort the list by size. All the empty groups will appear at the top of the list. The list will contain all groups, even empty regular groups that you want to keep, so you’ll want to watch that you do not delete a tag or a group that you want to keep. The option-command-delete shortcut will delete items from a smart group list.
Or, my favorite obscure tip, is double-click the top-level tags group to open it and its children in a new windows. Then, View > As List. Sort in whatever way you want (e.g., by Size) and delete what you want.