Most users have spent hours highly customizing Obsidian to meet our needs and preferences via settings, themes, CSS snippets, plugins, etc. But whenever we add a new vault—or want to temporarily designate a folder as a vault to use Obsidian on the files inside it—that’s all left behind, as if we’re opening Obsidian for the very first time. The only workaround (see below) is cumbersome.
Add the option to store the .obsidian configuration folder as an Obsidian application folder rather than in a vault
Enable the designation of a “primary vault” and add the option to automatically use the contents of its .obsidian folder to configure other vaults
Continue to keep separate .obsidian configuration folders in every vault, but add an option to keep their contents in sync
Copy the hidden .obsidian configuration folder into any new vaults.
When any new configuration modifications are made, they either need to be manually duplicated in every other vault, or else the .obsidian folders in all the other other vaults need to be periodically replaced with the newly modified .obsidian folder.
A common pattern that is used is to have a common place to have the settings at the application level. Then each vault is allowed to override the individual setup. Gets a little tricky with plugin interactions but would be a place to start.