People have already created issues for the improvements you've listed. Upvote them to show your support or create new ones if these don't satisfy your needs:
- CI manual jobs ignore dependencies: https://gitlab.com/gitlab-org/gitlab-ce/issues/28396
- Start a discussion from a non-discussion comment: https://gitlab.com/gitlab-org/gitlab-ce/issues/30299
Re: your last point, I've pinged someone from our CI area to see if we already have an issue for that.
The first ticket is a bit different. Starting depending jobs automatically would be great, but I would be satisfied if I could just click a button "Start this job when dependencies finish".
But anyway, those are all quite old tickets and I know from talking with other developers that I am not the only one having a sore point. And I don't see much improvement in the last year or so.
Don't get me wrong - I still love the product and would like to see it get even better.