When grading short answers / essays, I'm unable to mark student's submissions for revision.
I suppose the extremely inefficient workaround would be to quote the entire submission in the assignment comments and point out errors there (without a text editor to help with formatting). Such an answer would not surprise me as every basic basic basic ordinary regular everyday classroom functionality issue I've had with Canvas has led to extremely inefficient workarounds.
I just want to be able to have my students submit short answers / paragraphs / essays, and then I can mark them for errors, and then send them back for revision before giving them a final grade --just like I do with every run-of-the-mill pencil and paper assignment...
Yes, but let's say a student receives a lower score on the 2nd assignment attempt, then the lower score is kept in grades, not the higher score, and there is no setting to change this.
I'm not sure what you mean by no way to change this. For me, I can put any number I want in the Grade box. I can also update this directly in Speedgrader.