I have a Taiko drum track with 4 Taiko drums, each on their own channel.
The score just shows one line.
How do I get it to show the 4 drums ?
You will probably need to either create a new drum map with one entry for each pitch, or use a pitched stave.
I made a new drum map, and it shows up fine in the keyeditor. In the score editor this drum map is selected, but nothing shows up in the score . Tried 5 line presentation, grid or single line.. - nothing 
Can you DM me the project?
Thanks for sending the project. I’ve had a look. Non-drumkit percussion is something that isn’t supported very well at the moment, because it requires custom instrument types, which we don’t yet have. The score is blank because the score editor needs the Instrument Type field to be set in the Drum Map. It is possible to set them all to Taiko (and I’ve changed the display note to C3) which will show the rhythms, but there is a limitation currently where all the drums will be shown on the same stave line because the drum note map needs all the Instrument Types to be different for Taiko 1, Taiko 2, etc (and that requires the custom instruments)
One workaround for this is to set Taiko 3 to some other percussion instrument (eg snare drum), which allows the taiko 1 and taiko 3 notes to be on different stave lines:
Alternatively, you could split this into separate tracks so that there’s only one taiko on each track.