Can a team share a workflow?

No. A workflow belongs to one person. There is no shared workspace, no second editor, and no role you can grant a colleague so they can approve on your behalf.

This runs deeper than a permission setting. Every run, connection, example and record is scoped to the owning user, and a workflow acts with that person's access rather than a shared account. It is the same mechanism that keeps your workflows private from colleagues in the same organisation, which is usually the first thing people want and the second thing they run into.

The upside is that accountability is never ambiguous. One named person stands behind what the workflow does, gets asked when it needs a decision, and appears in the record afterwards.

The cost is equally plain. There is no way to hand a workflow to somebody else, so a workflow does not outlive its owner's account, and a process two people run together has to be owned by one of them. If that matters for the process you have in mind, say so early rather than late.