Rather than setting up another repeater region, I just switch on mouse broadcasting when I'm ready to complete the trade. Only the 2 involved toons have anything significant in the region of the trade button.
That's also how I do it. I have a toggle for mouse broadcasting mapped to scroll right on my mouse so it is very easy to flick it on with my index finger, click the LMB and then flick it off again. I also use a honking big, non-interactive click bar button as a visual indicator of when repeater is on.

Quote Originally Posted by Twyman View Post
I haven’t played around with setting up a repeater regions yet. I guess it’s time to try.

The mouse repeater option doesn’t seem to work well. My main computer screen is a wide screen, while my alt computer screens aren’t. So the mouse repeater isn’t exact enough for it work.
I believe the aspect ratio of both windows needs to be the same for this to work reliably. You can use a window layout with "maintain aspect ratio" to achieve this or set the sizes manually. Of course, this may mean you are not using all of your screen real-estate so you will need to decide which feature is more important to you.