How to delete RW themes?

When checking my themes in RW Classic I found a lot of outdated themes from years and years ago. I think these were themes provided by Realmac Software. Most of them are not responsive and there is no need for me to use them any longer.
How can I delete those outdated and unneeded themes in RW Classic now?

Thanx for your answer(s)

Try right click on the theme and select show in finder, then drag theme(s) to trash. I think you may be able to disable thru preferences as well.

thank you Anon for your reply, deleting a theme as you described it only works for non RW themes. Unfortunately most of the outdated themes are RW themes (back to about 10 years).
Unchecking them in the Prefs will at least remove them from the window of possible themes in an RW project but the theme data itself still is somewhere within the program file, I assume.

Yes: The built in themes reside within the Rapidweaver .app file.
It would be futile to remove them, as they would be restored on updating the app.

Best bet is just disable them in RW preferences. You can disable them all or individually :