When using the "Add User to Channel" for Slack Action, we need to be able to dynamically choose both a channel name and a person (possibly by email or username). Without it being dynamic, the action isn't useful in any real scenarios.
Sincere apologies for not getting back to you sooner. In case you haven't seen it yet, we have added this feature in Workato for both the channel name and user name. Just toggle as shown in the screenshot below.
Do try it out and let us know if you encounter any issues!
Send us a ticket, we will try our best to assist you with your problem