Isn't that a feature specifically of this theme?
Re the single mixer channel on left...you can just dock the mixer over there and adjust to fit a single channel (make this a screenset so you can easily switch to other multi channel mixer setups)
This can also show FX inserts and sends so maybe the thing you ask about is not also required.
Or there is Heda track inspector
https://forum.cockos.com/showthread.php?t=174202