That’s a question for @chad, I think. It’s also possible that there’s a 3rd party app that’d allow you to upload timed posts.
There is already a built-in post scheduler but the official apps don't have an interface for it. However, third party apps like Tusky and Fedilab do.
To answer the original question, there are lots of ways to participate as there are so many aspects to this place:
Mastodon is just one type of server, there are many other compatible types made by other people such as @gotosocial or @calckey or @pixelfed etc etc.
Then there are third party apps for most of them which may have extra features lacking from the core platforms.
If you see a project you're interested in, its website usually has a contribution guide.
I use timed posts with the @Tusky App. I like it.
That comment aside, my advice on where to engage and do feature requests of this nature is in the developer section of the software itself.
That would typically be located on GitHub.
You can view those discussions on the Mastodon software here: https://github.com/mastodon/mastodon/issues
For example, I shared an issue on the Tusky App in January: https://github.com/tuskyapp/Tusky/discussions/3150
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