How can I condense the vertical spacing of a system with multiple grand staffs, etc.??

Using MuseScore, I have entered as a musical system the following: a grand staff for a piano part, followed below it by a grand staff for an organ's manual keyboard, followed finally by a bass staff for the organ pedalboard at the bottom. For most pages, the vertical spacing top-to-bottom is great, and in each of those cases two systems of the above-described arrangement fit nicely on a page. However, in one instance only one system is present on the page. In that instance, the vertical spacing, top-to-bottom, is very inconvenient for playing, due to the extra large amount of space that appears between the two grand staffs and between the organ grand staff and the bass staff the follows for the pedalboard. This is particularly an issue for the organ player, because there is so much empty space between the grand staff for the manuals and the final bass staff for the pedalboard. (I see this also as an issue for the director who will lead the music.) So..., is there a way to control the amount of vertical space that appears between the various staffs? The default seems to be to use up AS MUCH space as possible to fill the whole page. I would much prefer to be able to control the spacing if the default become too difficult for the reader. Please advise. Thanks so much! Nolan W. Cook