I wasn't aware of Shift+F10 as a common alternative to the Application key. I thought that instead of adding yet another hardcoded special case for this in the places that have hardcoded custom behaviour for the Application key (i.e. the ones you observed where the Application key is working but Shift+F10 is not), we could turn this into a common, user-definable global shortcut (using Application and Shift+F10 as the default keybindings). However global shortcuts always have a higher priority than context-dependent shortcuts, and most famously since the early days OpenMPT by default binds the Application key in the pattern editor to open the Note Properties dialog instead of opening the context menu, and that behaviour would completely break with this implementation.

Maybe we can add context-specific shortcuts instead, I'll try that if I cannot come up with any other good solution. I don't really like that idea because it means the same shortcut configuration will be repeated several times if the user wants to change it.

Alright, through quite a bit of restructuring of keyboard handling code, there is now a good way to implement this.

As of r21624 (OpenMPT 1.32.00.25), the context menu key is now fully configurable. By default (if there are no conflicting shortcuts), both the Application key and Shift+F10 will be tried to be assigned when upgrading to this new version. At the same time, the Application key will continue to open the Note Properties dialog in the pattern editor if it was set up that way before. Note that due to aforementioned possible conflicts, you may want to double-check in OpenMPT's keyboard settings that this new shortcut ("Show Context Menu") is indeed bound to Shift+F10 (or any alternative key bindings you desire).

As said, this involved quite a lot of fundamental changes, so it will not be backported to OpenMPT 1.31, but definitely more testing is required if nothing broke. To try it out, you can set OpenMPT's update channel to "Development" or download a (portable) test build from https://builds.openmpt.org/builds/ as soon as it's available (may take a few hours).

I'll mark this as resolved for now. Feel free to reopen or file a new issue if you find anything not working with this feature in the latest development builds.