Close Tab synced between master

[Lettermin]

Redirecting a wish/question from the Glyphs forum: Is it possible to enable syncing CmdW for the Sync Tabs plugin? I use it frequently, sometimes with four opened master files, and my main problem is closing a tab in master one and then jumping to master two (where the very same glyph is still active in the tab), which opens it automatically in the other one. So I'm cruising between windows, clicking on the main 'Font' tab, and it is annoying.

[Mark2Mark]

One question though, maybe it's just the nomenclature that confuses me a little:
Why do you have different masters in different font files? I assume those don’t belong to the same font, or do they?