Hi @anderson.wong, you can’t prevent the trigger from starting your workflow, but inside your workflow you could query already running executions before doing anything else.
This uses n8n’s UI API so is rather hacky and can change without notice. The basic idea is described here, however the authentication has changed slightly (see this post for an updated authentication example). You might also need to check if the endpoints haven’t changed since this came up.
Make sure to also vote on the respective feature request suggesting a proper implementation of such a check: