A newly generated visual comes with a review bar underneath it. It is there so you can give a quick verdict without leaving the page, and it only ever appears for you while you are editing. Students never see it.
Accept
If you are happy with it, click Accept. The bar goes away for good and the visual is just part of your lesson.
Edit
Edit takes a plain instruction, for example "make the pendulum bob red" or "add a reset button". Only what you asked for changes; the rest of the visual is left exactly as it was.
While the change is being made, the current version stays on the page, so you are never looking at a gap.
Discard
Discard asks what you would like to do instead:
Try again rebuilds it, which is the one to reach for when the visual works but is not quite right.
Delete removes it from the page.
Cancel takes you back to the review bar and changes nothing.
Coming back to a visual later
Once you have accepted a visual its review bar is gone, but Edit and Try again stay available from the block's menu, so you can revisit it whenever you like. Using Try again from there does not undo your earlier Accept.
How this fits with the agent
If you ask the agent for a change that only touches a visual, it is applied straight away. There is no accept or decline step, because you asked for that specific change and you can watch it happen. A request that also changes other lesson content still goes through the usual review.