Within your Automated Workflows you have the ability to change the sending status or the active status of each message as needed. You might want to leave a message in an inactive or draft state if you might want to use it later and don't want it fully deleted.
To change the workflow sending status, you will need to go to your groups section and click on the Automated Workflows sub-tab.
You will now see a list of Automated Workflow steps for that group. Click on the name of a message in blue to open and adjust the status and details as needed. All messages with a green dot are active and will send. All messages listed with a red dot are inactive and will not send in the schedule based off a person's joining the group.
To activate the message click on the Activate Step button in blue.
To Deactivate a message that is active, click the Deactivate Step button in white.
You can reactivate and deactivate as much as you like, but keep in mind that the ones marked in red will not go out when a person joins the group, only the ones that are active and marked by the green dot.