Just like there is a "Lists" custom field, there should be a "Spaces" custom field.

We have a separate space for each client.

All folders and lists under this space are named the same.

So having the "List" custom field doesn't help for a task in multiple lists, because it just shows "Maintenance, Maintenance, Maintenance" as the different lists where that task exists.

Having a "Spaces" custom field would enable us to see the project task and the "client" (via a "Space" custom field) that it relates to.