Alterations to the forums are unlikely. Particularly for something that could be replicated with copy and paste.
Unfortunately... The closest to that right now is, """Deleted""" Blogs (More like hidden and unlisted, essentially it becomes only accessible by a shared link. You can edit them and stuff) For example, https://forum.novelupdates.com/blogs/leanans-dungeon-logs.4097/ Your profile's about section Copy + paste
Ok so you mean like a draft feature similar to emails? I dunno dude... I think this forum is built upon an existing product or feature.
They are not reliable, if you save the draft and post another post the original draft can get deleted. Currently I usually use word doc. That's why some time you see me writing with some time screen shorts from word.doc.