Thanks for the mention @Bastien_Siebman! No worries, @David_Harrington I’m happy to bring a bit of clarity here!
This “merge” option (https://asana.com/guide/help/fundamentals/accounts#gl-merge-accounts) allows you to access different spaces (Workspaces/Organizations) from a unique account, you will be able to easily switch from one space to the other following these steps: https://asana.com/guide/help/fundamentals/about-asana#gl-switch.
That said, each of your Organizations/Workspaces will remain completely independent. For example, your colleagues from Organization A will not see that you’re a member of Organization B and vice versa.
Essentially, merging your accounts allows you to maintain different spaces while keeping them completely separate, all from one single account!
Hope this helps, but if you have any follow-up questions, please let me know!