Audio Mixer jumps out of "Edit in Play mode"

Maybe this is intentional design, but when I press successively on the "+" button to create more Audio Mixers, while "Edit in Play mode" is enabled, the Audio Mixer goes out of the "Edit" mode.

To reproduce:
- Open attached project and launch "test" scene
- Open an Audio Mixer window and dock it
- Hit Play
- Hit "Edit in Play Mode"
- Click the "+" icon on "Mixers" tab more than once
- Observe that the Audio Mixer goes out of "Edit in Play Mode"