Ordinarily, it'd be quite simple, however, due to a MusicXML oversight in MuseScore v3.6.2,
it's not. I'll talk about the margins first and staff spacing second.
The settings are located in
Format -> Page Settings... and the checkbox
Two sided should be unticked. Unticking this means we have one set of margins for every page, which is what we want! Unfortunately, once exported to MusicXML, the margins will be separated between even and odd numbered pages, which is a problem if your left and right margins aren't equal because MuseScore is built so the left margin on odd-numbered pages is
always the same as the right margin on even-numbered pages, which is not what we want.
If we just tweak the values here, when we import into Finale, we'll find a small left-margin and a fat right-margin on even-numbered pages and it doesn't look good.
How to overcome this? First, experiment with what values you want in the Page Settings menu,
but don't set them here! Now, save the style you currently have by going to
Format -> Save Style... and save it somewhere and remember where you saved it! Next, open that file you just created in a text editor like Windows Notepad, Notepad++, Sublime Text, VS Code, etc. It's okay, it's just an XML file, which any text editor can read.
When you open it, it'll look like this:

Fortunately, what we're interested in is right at the top.
The values we want to adjust are right at the top of the file. I'll now explain them.
- pageEvenLeftMargin (line 7, in the image) - this is the page's RIGHT margin's value in inches. If you want to adjust the page's RIGHT margin, change the number between the tags.
- pageOddLeftMargin (line 8, in the image) - this is the page's LEFT margin's value in inches. If you want to adjust the page's LEFT margin, change the number between the tags.
- pageEvenTopMargin (line 9, in the image) - since our sheet is not two-sided, we can ignore this value.
- pageEvenBottomMargin (line 10, in the image) - since our sheet is not two-sided, we can ignore this value.
- pageOddTopMargin (line 11, in the image) - this is the page's TOP margin's value in inches. If you want to adjust the page's TOP margin, change the number between the tags.
- pageOddBottomMargin (line 12, in the image) - this is the page's BOTTOM margin's value in inches. If you want to adjust the page's BOTTOM margin, change the number between the tags.
If the values you want are in millimeters, you'll need to convert them to inches and then enter them.
Ask the omniscient Google if you need to!For example, suppose I want to change the right margin to 0.5 inches. Then, what I'll do is go to line 7 (where it says
pageEvenLeftMargin) and replace the 0.590551 with 0.5 and then save the file.
As another example, suppose I want to change the top margin to 14 millimeters. First, I'll Google what 14 millimeters in inches is (0.551181 inches) and then, what I'll do is go to line 11 (where it says
pageOddTopMargin) and replace the 0.5 with 0.551181 and then save the file.
After you've made your adjustments, make sure you save the file and then go back to MuseScore and reload the style by going to
Format -> Load Style... and selecting the file you just modified. That's it! Yes, it's tedious. Yes, it's hacky. Yes, it's annoying, but until that bug is fixed, it's the best way unless you want to modify the MusicXML file every time you export.
So, in summary, here's the method:
- Experiment with the margin values in MuseScore, but don't save them.
- Save your style by going to Format -> Save Style... and remember where you saved it.
- Open that file you just saved using a text editor like Windows Notepad.
- Convert your desired value to inches by asking the almighty Google, if necessary.
- Replace the number next to tag corresponding to the margin(s) you wish to tweak with what you want.
- Save the file.
- Reload the style by going to Format -> Load Style... and selecting the modified value.
- Done.
Oh yeah, if you want to modify the staff spacing, that value is in the same file, right at the very bottom.

It's the value called
Spatium (line 1269 in the image) and its value is in
millimeters, not inches. Basically the same approach as before applies.
- Experiment with the values in MuseScore, but don't save them.
- Save your style by going to Format -> Save Style... and remember where you saved it.
- Open that file you just saved using a text editor like Windows Notepad.
- Convert your desired value to millimeters by asking the almighty Google, if necessary.
- Replace the number next to <Spatium> with what you want.
- Save the file.
- Reload the style by going to Format -> Load Style... and selecting the modified value.
- Done.