mouse modifier
Please add keyboard modifiers for mx mouse buttons.
Holding the shift key on my mac could completely change every single button on my mouse.
For example: By default, I would have the side buttons assigned as forward and back. but if I held the shift button down on macbook, then the buttons would be assigned to copy and paste.
I've read many many posts, going years back, of other people suggesting a similar design feature.

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John Odunayo commented
yes, please i also need this. In fact, i expected this would be the case when i was getting the MX Master 3S (windows). Really disappointed to find there's a limit of only 15 controls. Adding modifiers would open up the controls to as many as possible (Shift+Forward would be different from Ctrl+Forward, Ctrl+Shift+Forward, and different from just Forward).
At the very least, you should create something like a progressive disclosure to reveal this options to power users.