A plugin cannot set the main statusLine, but its settings.json may set subagentStatusLine, which replaces each row of the agent panel. The input is a tasks array (id, name, description, tokenCount, …) plus columns; the output is one {"id","content"} JSON line per row.
The hook already records each subagent's DID by agent_id. If a task's id is that agent_id (unverified), a vibescrobble statusline --subagents could keep the default description · tokens and add the subagent's emoji. The plugin then shows it with no settings to edit. Check first that a plugin default does not hide a user's rows they would rather keep.