3-button mouse Amiga question...

[lasatex]

Hi, just as an Amiga user in the 90's I've never heard of a 3 button mouse for the Amiga, nor seen one...Looking at the schematic of the Amiga and especially the DB9 mouse port I noticed it is supported on the pin 5... but the question is: what was the middle mouse button for? Has it ever been supported by any program?
Thanks to anyone who can give me some info.

 

[jurassicman]

There is a nice commodity, called MXButton if I'm not wrong (I can't check that at the moment), that I always use in my systems and that I configure in order to close a window by double-clicking on it with the middle mouse button. I really like it.