How do I stop voice typing from muting/pausing other playing media? I sometimes want voice typing to transcribe voice audio that is playing on my device. However, whenever voice typing is started, it stops all audio coming from my phone.

I have the xposed module app settings installed. This permits you to revoke individual permissions for an app. I tried revoking media_content_control and modify_audio_settings, but this didn't do anything.
As you know the voice typing feature works by listening to microphone of the device in use and any device where you use voice typing would behave same as if the device keeps playing the audio and also try to listen to microphone at the very same time, it may end up listening to the audio that the device itself is playing and would cause conflict between the user's voice or external voice and audio played by device
Generally this is the standard way voice typing work on any device not only android, i just tried this thing on windows Cortana and it reduced the speaker voice to very low level while the conversation was going on
In short i guess that wouldn't be possible without going too deep inside the system and modifying system files