Thanks for sharing the feedback! The new frame design is, I acknowledge, a disruptive change. You're right that closing then waiting for a new one is not very practical. I agree.
We are iterating on the design with a goal of having uniform controls and behaviors across all frames, where appropriate.
The "top frame" or "editor" is special because that's where all interaction starts, but it is just another frame.
We'd like to separate "frame level" and "frame content" controls. Something like the broom control you suggest could be "inside the frame". That could enable both behaviors.
The "close" button was added for uniformity, and to clarify the behavior of the "eraser" icon. The action is to "discard" or "close without saving" the current frame. There had otherwise been problems when a saved query was edited and users wanted to abandon those edits. The animation is meant to reflect the action. We'll look at improving it.
Would you be interested in providing feedback about designs as we work on them?