Changing master port in switch configuration (RB751)

I have 751G 2HnD with default configuration.
Let’s say I want to change master port from ether2 to ether3 and leave everything else as it is. What is the easiest way of doing it? Let say its a hypothetical question.

But if it would be easier to understand my question, I want to disable ether2 due to malfunction.

Solved.
Using Webfig, i didn’t make changes in the right order. I was either tring to change existing port in bridge (from ether2 to ether3) or I made a new port (ether3) in bridge and than tried to make it the new master by disabling ether2 in the interface menu. The right order is:
-create new port in bridge
-disable/remove old port from bridge
-(optionally) remove ether2 in interface