Set up Workflow targeting rules, build out any branching, and apply rule conditions using the Team capacity condition.

Specify a team and whether or not you want this Workflow to match based on the team having capacity (one or more team members without conversations assigned) or not having capacity (all team members have conversations assigned).

Trigger a Workflow with Audience rules based on your team capacity for handling conversations.

Create a branch mid-Workflow with a Team capacity condition, then create the appropriate path for them to follow based on this capacity.