Do you want to schedule your posts on Mastodon so that you write them now and they are automatically published later?
Some third party apps including Tusky and Fedilab have a built-in scheduling option. Fedilab also runs a website at https://plan.fedilab.app which lets you schedule posts.
If you want a professional scheduled post management system, there are third party commercial services such as https://publer.io and https://buffer.com that now include Mastodon compatibility.
Do you mean a scheduler? Or something else?
Posting frequency for what? A repeated message?
Ah, interesting situation.
As far as I know the only options with advanced scheduling stuff would be third party commercial services like those linked in the original post? They seem to have queue systems.
For what it's worth, I've heard toot is very useful for automated scripts.