Can I chain multiple edits together?

Yes, on the Pro and Team plans. After a job completes, "Build on the last result" above the request box is ticked for you, so your next request edits the drawing that job produced. Untick it to start again from your original upload. You can chain as many edits as you need. On a trial or the Starter plan, every request starts from your original upload, so ask for everything you want in one request, or repeat the earlier change alongside the new one.