The developers strongly advise against any use of nested vaults, warning that the program is not designed to cope with them and things may break.
(Nested vaults are vaults located within another vault. As with any folders, It is possible to have many layers of vaults.)
They do however, have some uses:
- They allow the same vault to be open in more than one window.
- They allow sub-folders (aka nested vaults) to use a different CSS to other vaults, and to have its own saved workspace etc.
- They make it easier to focus on the material in the nested vault without being distracted by other files and folders.
- They are very useful for projects where most of the sources and writing is project specific.
To a vault at the top of the hierarchy, the vaults nested within simply look like folders, and all normal Obsidian functions are possible.
The nested vaults beneath cannot see, or be aware of, vaults above or to the side of it in the folder hierarchy.
My preferences, based on observations thus far, are:
- Avoid nesting a vault unless the gain from having one is clear.
- Editing and linking at the top level should be safe for everything.
- Unique file names are essential - but clashes may not be pointed out in a lower level vault - so have another way of checking uniqueness if creating new files in a nested vault.
- Using links in a lower level vault is likely to lose data except when the links used are all within the vault. If you try to use a link to a file in another vault, it cannot be found and can trigger the creation of a new file of the same name within the vault. Therefore only use and make links with files in the vault.
- Conversely, it is best for each vault to have its own attachment folder. This keeps everything relevant in one place, making it easier to manage from the OS file system and works perfectly well from higher level vaults.
- There is no risk when a nested vault is used only in preview mode; this can be useful when you want to read in one window and write in another.
- Have a robust backup routine.
- Have programs that can compare files in folders and identify changes - if there’s a problem, version control ala Dropbox etc may not be sufficient to recover the situation.
- They work best where the material in the nested vault has little interaction with other vaults. Little but not none - if it were none there would be no reason for it not to be a completely separate folder. And a lot of interaction means it would be better to have access to them all.
I don’t use markdown links and I use shortest path (usually) - I can see that either of those might make a difference.
I would be keen on corrections, additions and observations. This is a topic rarely discussed, presumably to avoid encouraging users to do something inherently unsafe. Equally, I’m aware that a number of people use the technique, so establishing safe boundaries and known risks may be useful.