LogiGamer mouse profile software lets you assign keystrokes (or any other command) to all of your Logitech mouse buttons. Why Logitech doesn't let you do that in their own control panel, who knows... The program has two parts: a profile editor, and a lightweight profile switcher that can detect what's running and load the right profile for it. Be aware that the most current info seems to be in the forum, including the link to the very newest version. Read the first post in that thread, there are a few manual installation steps.

Tip: in Logitech SetPoint, go to the gaming tab, turn on Game Detection, and make sure that "keep keypress button assignments" is turned on. Otherwise, keystrokes assigned to mouse buttons don't seem to work.

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