tldr; Try swiping across the folder in the list view. Or see the button in the next update.
It seems the most frequent confusion people have when using TrustyBook is how to delete folders. I’ve gotten a number of bad reviews because people think it can’t be done. The feature’s been in TrustyBook since I implemented folders, which was so long ago I don’t remember if it was after the first release, or when I was playing around with the original code on a train between Portland and Seattle, months before the world saw TrustyBook.
The general confusion this seems to have caused is really highlighted in John Gruber’s frequent likening of gestures to keyboard shortcuts (regarding the home button, close buttons). If a feature is only accessible via a gesture, even if it’s a standardized gesture, it’s effective hidden. It’s interesting to think that all the people who didn’t know how to delete folders in TrustyBook likely don’t know about the widely-used swipe to delete gesture across all iOS apps.
I made a video demonstrating the swipe gesture in TrustyBook and put it on the app’s support page ...