Which version are you using? It is working for me in PADS VX1.2 but I don't have PADS VX1.1 installed to test it and the mapping is different in Xpedition VX.1.1. The other key mapped to this is 'Home', does that work?
Based on another thread you have going I would guess the F4 key is overwritten. My default "ViewSelectionFilter" shows no shortcut key, where yours shows Ctrl+F4 - which leads me to believe the plain F4 is also overwritten.
You could try the Help > Show Bindings - but I don't think that shows bindings created in WDIR locations. You will probably need to take a look at the version specific WDIR and check those locations for the key binding vbs file (the name is dependent on the flow and project type) to see if you can find the overwrite/definition.