How to activate the chat menu item in whatsapp web version?

Question

Mozilla Firefox

I am creating an extension for the Firefox browser that automatically downloads images to disk.
Everything turned out, everything works fine, but only if some interlocutor is active.
Now the task is to go through all the interlocutors - activate them from the menu.
But not a single event works, click, mousedown, dragstart, etc. !
I am surprised and confused. Help, tell me, I'm ready to pay for it.
Web version - https://web.whatsapp.com/