Obsidian vaults cannot be stored in custom folder locations on iOS.
This decreases the storage flexibility of the vault contents. For example, it is not possible to store the vault in a folder being synchronized to a third party cloud provider.
Personally, I like to use a third party storage service and sync files with Cryptomator. Cryptomator creates a separate folder where data can be stored in. This is the main reason I cannot add any Obsidian vaults in there.
Allow vaults to be created and opened from custom locations.
This will allow the vaults to be present in folders and paths that are not decided by the software itself.
The only options I can see are to give in and use iCloud/Obsidian Sync or have some Git solution.
I’d really prefer just to create a vault in any folder that the user specifies.