Please, no, I get flashbacks from my 6-month journey (still ongoing...) of the code review process I caused/did. Keeping PR scope contained and small is hard.

From this experience, I wish GitLab had a "Draft of Draft" to tell the reviewer what the quality of the pushed code is at: "NAK", "It maybe compiles", "The logic is broken" and "Missing 50% of the code", "This should be split into N PRs". This would allow openly co-develop, discuss, and steer the design, before moving to nitpicking on the naming, formatting, and/or documentation details of the code, which is likely to drastically change. Drafts do work for this, but the discussions can get uncomfortably long and convolute the actual finishing of the review process.

Once both reviewer(s) and the author agree on the code design, the "DraftDraft" could be collapsed into a link in an normal Draft to be mocked next. The scope of such draft would be limited by the earlier "DraftDraft".