When I search something in the modular storage UI and close it, the text remains when I reopen it. It also remains if I right click to clear the text, the only way I can make it disappear is using backspace to delete the text, which makes searching a nusiance.

The fact that it remains when you reopen the UI is actually a feature. I might make this optional though in the future. Right clicking to clear the text should work however. Where are you right clicking exactly?

Found and fixed for next release of rftools 3.31