According to FireyMerlin in the wow channel in the ISBoxer discord, they were able to send a /setview macro to all characters at once using addon messaging. Is it actually possible to add a (or multiple) setview /click, or /ema macro that would work on all slave toons at once?

My guess is this isn't done in a macro, the API is just unprotected and allows addons to do this:

https://wowwiki.fandom.com/wiki/API_SetView