Jujutsu: a new, Git-compatible version control system

Yes you can!

(a) Interactive rebase to the commit in question (called "sha1" below),
(b) Revert the parts you don't want to be part of the first commit.
This can be as simple as "git show -- path/to/file/ | patch -p1 -R" if you just want to revert all changes to one file, or "git show > d", "vim d", "patch -p1 -R < d" for more complex cases.
(c) "git commit -a --amend", to edit the commit message for the first part,
(d) "git cherry-pick <sha1>" to pick up the remaining parts,
(e) "git commit --amend", to edit the commit message for the remaining parts.

To split in more parts, have more b/c/d steps in between a and e.