if you are more comfortable with setting keys to mouse button 1 mouse button 2,3,4,5 etc you should not buy that mouse.
I wait for that option since 2018 now, because I am ONLY able to bin keyboard buttons to the mouse button in the software. better buy a crap mouse. they often have also 4 buttons but in option it say clear: mouse button 1 mouse button 2 mouse 3 mouse 4 etc and not mouse bottun 1= keyboard button "R", mouse bottun 2= keyboard button "@"