- there is no multi-select of items in the layout list
- every deletion must be confirmed
- I'm cleaning up, i.e. deleting old layouts, and I have over 1000
- I'm going to get RSI from this activity !
you can prob do it from the filesystem.
%APPDATA%\GPSoftware\Directory Opus\Layouts
wowbagger's suggestion is probably the easiest way to delete a huge number of layouts, and should not cause any problems.
From the UI, you can also delete lots of layouts in one go by moving them into a folder, then deleting the folder (but that will only save you the confirmations, not having to click & drag each layout individually, so the earlier suggestion is still better for 1000 layouts):