I would also like to bump this feature request. I use Obsidian for my personal notes, and are now using Obsidian for my school notes that are backed by github and shared between some classmates.
I cannot share my personal notes with my classmates, so this usage requires two vaults. I’m not a huge fan of having multiple windows because that would require me to set two different themes, otherwise I’d constantly be confused on which one is which. I’m also not a fan of cmd+~ to switch between instances of applications.
It would make more sense to be able to open multiple vaults in the same window, and switch between them with the standard cmd+shift+[ and cmd+shift+].
I suppose that means you’d probably want to move the Theme settings into a global preferences store, and have an option for per-vault themes that switch when you switch vaults (performance issue on load times maybe? Though I bet you can just cache it…)
Anywho, I’d love this feature 