hi yanus, looks like middle mouse button is permaset to pan

"Middle click for Pan, and the scroll wheel for zooming"
https://moi3d.com/wiki/Shortcut_Keys

I searched through the moi ini "mouse" but didnt see a middle click setting
Maybe there is an ini setting or option could be introduced..

Not tested but maybe this might help:

X-Mouse Button Control (XMBC) is a free tool for Windows that allows
you to re-configure and remap mouse buttons to expand the capabilities of your mouse.

https://www.highrez.co.uk/downloads/xmousebuttoncontrol.htm

im sure theres other tools. Also nearly all current Logitech mice
with a physical middle-click (usually activated by pressing down on the scroll wheel)
are programmable. However, button customization depends on the model's software family.

cheers

stefano