If it’s just one instrument and not an instrument in a score, Layout Options/Vertical Spacing/Braced Staff to Braced Staff: 2 Spaces and Vertical Spacing/Minimum Gaps/ uncheck “automatically resolve collisions between adjacent staves and systems” should do it. Obviously that will screw up a lot of stuff in a score with other instruments. You’ll have to up/down arrow to switch between staves while inputting but that’s not too much of a hassle. Shortened stem rules are also shot so you’ll have to do a bit of tweaking there too.