Carve off a bit of an stl file

Hi All…

A friend wants to replace their Valance Clip. I found one .stl file that closely remembers theirs but it needs to be a little less wide.

makerworld.com/en/models/993954?from=search#profileId-969928

He shared if I could “lop off” part of it that might fit.

How can one carve off a piece of an ‘stl file?

If not, is there a tool simpler than On Shape or Fusion 360 to do that?

Thank you