How do I use a different name or email for one repository?

Innesta does not keep an identity of its own. It commits with whatever git resolves for the repository, which is the repository’s local configuration if it has one and your global configuration otherwise.

So a repository that should use a different address gets a local setting:

cd ~/Projects/that-one
git config user.name "Ada Lovelace"
git config user.email "ada@work.example.com"

Commits made in Innesta from then on use it, because Innesta drives the same git.

The global identity is the one onboarding asks for, and the one everything else falls back to. Innesta writes it that once and does not offer to edit it again, so changing it later is git config --global too.