If you are a member of multiple organizations or teams that use Reduct, you can switch which workspace via the user menu by clicking on your profile in the top-right corner of your screen.

Note that you may not see this menu if you aren't a member of multiple workspaces.

After clicking on the current workspace (in this example, clicking on "Syntax Industries"), you will see all workspaces you are a member of, listed underneath. Click on one to switch to it.