Current drum notation is lacking usability. As there are no actual "standard drum notation", rendering must be a configurable mapping allowing to define a link between percussion instruments and rendering methods (e.g. a song may use 10 different toms, placed in a certain pattern on the staff whereas another may map triangle, cymbals and congas in the same staff space). I am aware that currently TG is currently limited to midi values to define percussion instruments and that should be fine for most use cases. If there is really a need, one can replace missing instruments by an unused midi number (e.g. "rim shot"->"hand clap") and define a drum mapping, if one only cares about the resulting notation.
I have hacked the attached patch, which outlines how I think percussion should be mapped on the staff. It should be fine with simple drum scores (2 cymbals, bass drum, snare, 3 toms, high hat).
The provided mapping class should be flexible enough to allow loading "drum profiles" from config, though not implemented in said patch. (I'd need to discuss with you the most appropriate method of config storage for those mappings)
Don't hesitate to contact me to discuss any of this. Also I am willing to contribute more code related to this feature, if resources are needed.