Is it possible to downgrade a license?
(considering the warning on the upgrade page: Upgrading means the license(s), indicated below on the left, will be removed and will be replaced with the license(s) shown on the right.)

Background:

I'm in the process of upgrading (my plugin and - if successful - Studio) from 2017 to 2019. I have Freelance Plus license for 2017 and bought an upgrade to 2019.

I have Studio 2017 installed on my "translation" PC and a "develop" PC (which I also use for holidays). I would like to upgrade 1 of them (dev) to 2019 but stay on 2017 on the main PC. Is this possible?

Alternatively: Could I "toggle" (upgrade/downgrade) licenses between 2017 and 2019 while I develop my plugin?