How can I use the F14 and F15 key for a shortcut?

Yes, F14 and F15 change my screen's brightness. I never set this up. I have brightness keys on F1 and F2, so the redundancy is very annoying since I used to be able to assign custom window sizing tasks to these keys.

I've actually managed to assign a window resize task to F15, though can't get F14 to do anything. Still, I can't remove the screen brightness control from F15. So when I resize the window the screen also gets brighter. This is clearly not a usable shortcut.

Also, when I open the keyboard viewer it only indicates key presses for F1-F13. F14-F19 don't register on the keyboard viewer.

Apologies, I only meant to post in the Mojave area and the High Sierra area. I believed the first attempt I made to post was unsuccessful, so thought I had the question out to two communities only.

I've just now found the area where I can see my posts and there appears to be two instances of my question.

Ok, I will avoid repeating myself.

As for the keyboard. I am using an Apple Magic Keyboard with Numeric Keypad. I have no third party keyboards, though I read somewhere that using one was the only way to gain access to the "display" section in Keyboard>shortcuts, where this redundant F14, F15 is controlled.

THat's what I was previously reading; there's a control for these keys at System Preferences > Keyboard > Shortcuts > Display, but you can only access it if you have a non apple keyboard. I only have an Apple keyboard, so there is no such location in my System Preferences > Keyboard > Shortcuts.

BTW, I appreciate your efforts to try and solve this 🙂

No worries about the confusion. There are a lot of conversations going on.

Interesting that it's available with an Apple wired keyboard. I might be able to borrow one of those to switch these settings off then. Too bad it doesn't work when I plug in the Magic Keyboard in as this does override its wireless connection and make it a wired keyboard.