git rebase to _insert_ commits?

[Misha Koshelev]

Dear All:

I am still learning git and it seems that my solution does not quite
work.

Specifically, my idea was to use:
git rebase -i upstream/master

Mark the commit _after_ which I'd like to insert a commit with edit.

Then, when I am at that commit, I do:

git commit --amend -a

save commit

Then, _before_ doing git rebase --continue, I edit files and again do:

git commit -a -n

Finally I do:

git rebase --continue

The problem is that this seems to squish further commits, and leads to
problems which I am now trying to untangle.

However, as I still cannot insert a commit, I am not sure how to
proceed, except by creating a whole new repository.

Any ideas/hints?

Thank you
Misha