Thank You very much,

"xdotool click 3"
m:0x80 + b:1 + release

...work fine. That was my *facepalm* moment - I typed "click3", without space... I was so sure that it's how it looks like in Rebhana wiki, that I was about to report typo there - but i checked again, and that was just me 0_o

In my opinion, it works so great and reliably, that it should be default setting in ED.

By the way - sorry if it was posted before - when app (like Iceweasel) is started from outside LXDE, context menus work *only* when not in fullscreen. It's not that right/middle click or long tap doesn't work - it *work*, but context menu is just not shown. Switching back from fullscreen reveal "hidden" context menu. No big deal, but is it normal?