Moving lists between workspaces
You can move lists between workspaces that you are an owner or admin of by opening the preferences menu at the bottom of the left sidebar and selecting "Move Lists Between Workspaces".
This will launch a dialog where you can select lists from the your current workspace to be moved to the new workspace. Just select the lists you wish to move and click "Choose Workspace" to move to the next step.
From this next step, you'll be able to choose from any of the other workspaces you're an owner or admin of. Simply select your destination workspace and click "Confirm" to continue on to the next step.
If you need to invite new members to the other workspace, you'll be asked to set the roles of these new members before confirming the move. If this is the case, the "Confirm" button will say "Set Roles" instead. Simply click it to continue on to the next screen.
From this next screen you can choose the roles for each of the new members of the destination workspace, explained here. Once you're finished choosing the roles of the new members, you can continue to the final step by clicking "Confirm".
Finally, you'll be able to confirm the new lists and members to be added to the destination workspace. If you're happy with move, click "Move Lists" to begin moving the lists over.
Moved lists will appear in the destination workspace below your existing lists and groups in the sidebar. Once the lists are fully moved to the destination workspace, you can then start interacting with your lists as usual.
If you own the the destination workspace, you may run into the limitations of your plan by inviting new people to it. If this is the case, clicking "Move Lists" will load a small upgrade form where you can choose a better plan. If you do not own the destination workspace and run into the owner's plan limitations, you will not be able to continue.