Comment 56 for bug 62949

(In reply to Rob Kam from comment #48)
> Twenty years later and this is still unresolved?
>
> Going to System Settings > Input Devices > Keyboard > Advanced > Swap ESC
> and Caps Lock is a piece of cake.
>
> Then going to System Settings > Input Devices > Mouse there is nothing for
> changing e.g.
> Wheel Down > Screen down
> Wheel Up > Screen up
> Button Forward > Control + Left click
> Button Back > Shift + Left click

Well, when you're on Wayland, there is actually an interface for setting up the additional mouse buttons, but it only works for extra mouse buttons (10+) and not for those that are mapped by default (1-9).
And at least with the current versions even that is broken, e.g. you can assign a keypress event to a mouse button, but it won't work.
In principle if you would like to reassign buttons 8 (back) and 9 (forward), you could remap your mouse so that these are e.g. button 11 and 12 and then you should be able to reassign them to a keyboard combination you could then use. I haven't checked though whether this works, because as mentioned above it's broken.
And it should be possible to directly assign mouse buttons in khotkeys (bug 96431).

But in general I agree, it should be possible in the kcm to remap mouse buttons to different functions or even a key combination.
I would like to have a list of detected mouse buttons, each with a dropdown list and a couple of predefined mouse actions, e.g. the default mouse actions + selected commands (like those listed for the screen edges), e.g. present windows, peek at desktop, activity manager, close tab …
And as the final settings I would like to have "Mouse button 10" (if it's button 10) or "Use as hotkey", so that it can be assigned to any (possibly program-dependent) hotkey function and "Key combination".
Of course that also means that there is some duplication in the functionality, but I think it would be nice to present a selection of predefined commands to the user.

For me, these possibilities are – together with the problem of restarting kwin – the main showstopper to switch to Wayland.
On X11, I'm using imwheel, but that doesn't work on Wayland anymore. There are some options out there to get something like imwheel on Wayland, too, but they basically require working around the compositor and usually are way more complicated to setup, so I really would like to avoid those.
Plus, I think in 2023, it should be really possible to properly setup your mouse in KDE without needing to fall back to 3rd party programs. :/