Tried this in Edge and experienced the same issue. I'll keep testing to see if it's just my machine. ; )
I find that it doesn't work in 'Edit Mode', but works in 'View'. If I'm in edit mode and click on a link, it will replace the current screen, but in view mode, it opens a new window. I mentioned this in the feedback forum.
Sorry - I missed part of your post, so my response doesn't apply. Although, I haven't had the issue with adding fields, and I've created a lot of forms. I am also using Chrome and I'm on a Mac.
