In recent previews I can not use Crtl - to remove input pins from a RootScene. Adding input pins with Ctrl + works though. Also it seems to be only the case for the RootScene - for a Cons both adding and removing input pins work.
First broken version on my machine: 5.3-0080
Last working version on my machine: 5.23-0069
Confirmed also here, broken in preview 0231 still
Thanks for reporting and going back in time! Upcoming builds will fix this.
Just for reference, this was also broken in older versions when one enabled the optional “Child Scenes” pin. In 5.3 all pins are now stored on application side (including optional and hidden ones), that’s why this issue came up only now.