It's super simple.
Login to your organisation account
Click your organisation logo and name top left of the screen:
Click the plus icon and then create a new organisation (OR you can switch to another pre-existing organisation if you already have a second one set up).
Then you can add a second (or third, fourth, fifth...and so on) organisation to your account.
You can always access these using the same login, and each organisation is separate, so the admins in one organisation can't access the other, unless you also add them to that organisation too. It means you can set up feedback forms and certificates as different orgs, and to access them each time just hit "switch organisation" on your account.