mastodon.online is one of the many independent Mastodon servers you can use to participate in the fediverse.
A newer server operated by the Mastodon gGmbH non-profit

Server stats:

11K
active users

Marius

Dendron also includes a powerful refactoring tool, so you can easily change this hierarchy later.

I use Dendron with the PARA method (Projects - Areas - Resources - Archives), which requires frequent changes in the hierarchy with having to move inactive or completed projects to the archives, and it works perfectly