Connecting two staves as one instrument (but serparate staves)

I am attempting to write a piece in which a mallet player plays the marimba with one hand and hits a tambourine with the other. I would like to link the two instruments as if they were on a grand staff, something i found like the image below.
I cannot figure out how to do this. I can make them be in the same part, but not together like this, and never on the main score page. I know this is possible because it was done like this in the attached image.

(image is two different marimbas each linked to a separate percussion line