Pedal Diagram Plugin installed correctly, and will not open for use in any capacity.
1) Import plugin.
2) Enable plugin.
3) Open plugin.
The window should open and stay open for one to create a harp diagram. The plugin now causes a new window to open which nearly instantly closes.
I have not been able to get it to open for longer for any usable time frame, during which there are no details inside the window. I cannot figure out how to install a previous version of Musescore so I cannot see if this works there.