What is the hotkey that is bound to middle mouse botton?

Age of Empires III: DE Ask for Help
1

i dont find it on hotkeys , but when i press the button taht is on the scroll of mouse it selects my urban center
and i want to bind a new hotkey to my scroll button of my mouse (middle mouse button)

2

i think
last event .

3

what does it do? i used it and camera moved to a zone on the map then to another zone and finally to a antive post without building

4

check chat list
this is chat and event for u

5

it doesnt open chat, though. Do i have to have chat opened then use it? when i open chat last event is already there if i remember