When more than one mutant is open the bottom bar does not behave as expected
Example:

The last opened mutant is displayed in the bottom. If you now close one of the mutants the bottom bar disappears even though other mutants might still be open.

What should happen when 2 mutants are still "open".
This works as designed currently. I didn't want to go into that rabbit hole. It basically functions the same as the popover we had before.
I would expect that either only one mutant can be open at the same time OR the bottom bar stacks in the order the mutants are clicked open. Preferably the latter. Perhaps we could show them as 'tabs' in the bottom with a close button. Closing the bottom bar would also close the corresponding mutant and vice versa.
I would personally first try to make a better "diff" view (instead of the blue badge). Once we have that this problem might have been solved already, since it might not allow for multiple mutants to be open at the same time.
Until then, I'm personally happy with the way this works. It isn't the worst, sure it can improve, but I would rather spend that time on other important features for now 🤷♂️.