Giles,

           Thanks much for the additions to the list of "not problematic" add-ons as well as having identified two that are problematic with regard to the use of F4.

           I have tried to explain to my students that when any key is pressed, the first thing that gets a chance to "have at it" is the operating system.  If the operating system doesn't do anything with it then it gets passed to the next layer, and when a screen reader or other assistive technology is in the mix it gets it next.   If anything in that layer can process that key press, that's where it will stop being passed along, and that's even if that key press will do nothing in context when it happens to be pressed.  Once something intercepts it, and processes it, the key press does not continue through the hierarchy of processing any further.

            The more "stuff" you have running, and particularly a screen reader and a bunch of add-ons, the more likely it is that one of them is going to snag a key press that you "never use" when doing your day-to-day activity, so you have no idea that it's being snagged at that layer, until something at the application layer uses that key press, too, and you expect it to see it and act, and it can't, because the key press has already been snagged and processed before it ever sees it.

             I'd say this is probably the most common reason a screen reader user finds that certain application key sequences don't work, and it's not because of an application bug, nor even a bug in the screen reader or add-ons, but because things are actually working as designed with their defaults, which sometimes have to be changed.
--

Brian - Windows 10 Pro, 64-Bit, Version 1809, Build 17763  

Growth for the sake of growth is the ideology of the cancer cell.

           ~ Edward Abbey