Obsidian Sync: Manual allocation of available space among remote vaults

Currently, the available Obsidian Sync space is distributed equally in 5 remote vaults of 10Gb each.
It would be nice if the user could manually preselect how to allocate the available space (50GB): how many vaults and how much space for each vault.

This is similar in spirit to this FR, but space allocation is manual and premade as opposed to dynamically accounting for the space occupied.
Given the current backend infrastructure. this FR is easier to implement.

There are no plans to work on this in the short term. Should this change, it will be added to the roadmap https://trello.com/b/Psqfqp7I/obsidian-roadmap

Related FRs: