How to make a git branch from commita?

Question

git

for example, make a new step from m5

Answer 1

All the black marks on your screenshot are already branches.
So you already have the m5 branch. It just doesn’t have a single commit of its own yet, so it hasn’t been singled out as a separate step.
So that

git switch m5
# редактируем
git commit
git push

and the m5 branch will have its own step.

Answer 2

Stand on a commit, then git checkout -b