Thanks so much! Just to add on a bit, I was able to find that these are how the buttons are on the trackball:

--------- | 2 | 8 | --------- | 1 | 3 | --------- 

And this is the order they are in the ButtonMapping string:

LeftClick MiddleClick RightClick ScrollUp ScrollDown ? ? Back ? 

So, for me, I just wanted right and left on the bottom row, with back top left and middle top right:

Section "InputClass" Identifier "Kensington Kensington Slimblade Trackball" MatchProduct "Kensington Kensington Slimblade Trackball" MatchIsPointer "on" MatchDevicePath "/dev/input/event*" Driver "libinput" Option "ButtonMapping" "1 8 3 4 5 6 7 2 9" Option "ScrollButton" "8" Option "ScrollMethod" "button" EndSection 

The documentation here is non-existent, so this is what I could piece together by running xev -event mouse.

Thanks so much! Just to add on a bit, I was able to find that these are how the buttons are on the trackball:

--------- | 2 | 8 | --------- | 1 | 3 | --------- 

And this is the order they are in the ButtonMapping string:

LeftClick MiddleClick RightClick ScrollUp ScrollDown ScrollLeft ScrollRight Back Forward 

So, for me, I just wanted right and left on the bottom row, with back top left and middle top right:

Section "InputClass" Identifier "Kensington Kensington Slimblade Trackball" MatchProduct "Kensington Kensington Slimblade Trackball" MatchIsPointer "on" MatchDevicePath "/dev/input/event*" Driver "libinput" Option "ButtonMapping" "1 8 3 4 5 6 7 2 9" Option "ScrollButton" "8" Option "ScrollMethod" "button" EndSection 

The documentation here is non-existent, so this is what I could piece together by running xev -event mouse.

Here is a map from button ID to its function:

Thanks so much! Just to add on a bit, I was able to find that these are how the buttons are on the trackball:

--------- | 2 | 8 | --------- | 1 | 3 | --------- 

And this is the order they are in the ButtonMapping string:

LeftClick MiddleClick RightClick ? ? ? ? Back ? 

So, for me, I just wanted right and left on the bottom row, with back top left and middle top right:

Section "InputClass" Identifier "Kensington Kensington Slimblade Trackball" MatchProduct "Kensington Kensington Slimblade Trackball" MatchIsPointer "on" MatchDevicePath "/dev/input/event*" Driver "libinput" Option "ButtonMapping" "1 8 3 4 5 6 7 2 9" Option "ScrollButton" "8" Option "ScrollMethod" "button" EndSection 

The documentation here is non-existent, so this is what I could piece together by running xev -event mouse.

Thanks so much! Just to add on a bit, I was able to find that these are how the buttons are on the trackball:

--------- | 2 | 8 | --------- | 1 | 3 | --------- 

And this is the order they are in the ButtonMapping string:

LeftClick MiddleClick RightClick ScrollUp ScrollDown ? ? Back ? 

So, for me, I just wanted right and left on the bottom row, with back top left and middle top right:

Section "InputClass" Identifier "Kensington Kensington Slimblade Trackball" MatchProduct "Kensington Kensington Slimblade Trackball" MatchIsPointer "on" MatchDevicePath "/dev/input/event*" Driver "libinput" Option "ButtonMapping" "1 8 3 4 5 6 7 2 9" Option "ScrollButton" "8" Option "ScrollMethod" "button" EndSection 

The documentation here is non-existent, so this is what I could piece together by running xev -event mouse.