Hey there,
Unfortunately the answer is we will never be fixing this in the original BBM, we realized that the code was beyond spaghettified and could not be fixed or expanded upon without breaking several other things in the process.
The good news is we have started from a ground up on a BBM2 which is expected to have a much better volume management system along with a stronger drum creation and editing UI.
We know this isn’t the best thing to find out, that there is no solution, but this is why we have put a lot of emphasis on the new BBM, work has already began on this version
More news soon, stay tuned!