Though it wouldn’t necessarily take account of iPad use. Maybe a Shortcut could be used, though I’m not sure Shortcuts, like most of iOS, can see hidden folders.
Also, wouldn’t this method presuppose that one particular vault will always be the one to be changed, the one which seesds changes to others?
I think Shortcuts can see hidden files on iOS. I dimly remember this or something like it coming up here or in Discord — sorry I don’t remember better. I think @Calion was in that discussion? (Sorry for the ping if not!)
Is your Mac continually running? If so, just get some sync software to keep the .obsidian folders constantly in sync. You may even be able to get fancy and do something natively with Folder Actions.
Or…hm…what would happen if you made a symbolic link of one .obsidian folder into the other vault? That would work perfectly on the Mac, but I have no idea what will happen when it gets synced to iOS. It might just work!
I think it didn’t work yesterday for me when I tried it on the .obsidian folder itself (as opposed to a child folder). It kept saying the object had to be a folder rather than a file. Maybe it’s not seeing .obsidian as an anything, whereas child folders themselves are not hidden.
Here’s how it’s working between my vaults (3 on Mac, 1 on iOS):
There is one Main-Vault on Mac (which has the primary snippets directory).
There are 2 other vaults on Mac, which have Symlinks to that snippets directory. The CSS for these vaults updates after changes to the primary snippets file (but only after a reopen/Force-Reload of those secondary vaults).
There is also an iOS vault, synced (via Git) to that Main-Vault. It receives all updates from the main vault.
I imagine the same strategy could work for your plugins folder.
I use freesync to keep consistency between the main vault and the multiple different vaults and also the ones on mobile devices.
I use a different folder, i.e. .obsidian-mobile for mobile devices, because I found the workspace configuration used on desktop version freezes the mobile obsidian. So I use a different folder for mobile devices, esp. to store the workspaces used on ipad. And I think the synchronization between desktop and mobile needs to take the compatibility in the first place.
Every time, after the update of some plugins, I will perform a synchronization.
The 1st step of synchronization is to sync the .obsidian-mobile with .obsidian, which are both in main vault. They will be used to be synchronized to other vaults later. In this step, one can use a whitelist or a blacklist to filter the fils needs to be synchronized within the folder. I only sync the .obsidian/snippets and .obsidian/plugin, so that the configurations made on iPadOS will not be flushed.
The second step is sync the .obsidian and .obsidian-mobile in the target vault with the ones in the main vault. I use different main color accent for different vaults so that I can tell the belonging of a note on screen by a glance and will not take notes in a wrong vault. So in this step, i exclude /appearance*.json files in the .obsidian and .obsidian-mobile folder to keep the main color accent be what it was. This is the only tricky part, I think.
After the synchronization, the multiple vaults work in the same way, except the main color accent.