How do I add or amend field input tips for a plug-in once they have been created

If the smart service hasn't been deployed yet, then you just need to add the corresponding field and its setter in your smart service class. However, if this smart service has been previously deployed and you realize that it now needs more/less inputs/outputs then you will have to deprecate the previous one and deploy the new one with a different smart service key. The running instances will continue to work (but using the deprecated version), once you drag and drop the new node into your models then new instances will use that updated version.

As you can see if need to change inputs/outputs then this is considered a new smart service as explained in the documentation forum.appian.com/.../Custom_Smart_Service_Plug-ins

If the smart service hasn't been deployed yet, then you just need to add the corresponding field and its setter in your smart service class. However, if this smart service has been previously deployed and you realize that it now needs more/less inputs/outputs then you will have to deprecate the previous one and deploy the new one with a different smart service key. The running instances will continue to work (but using the deprecated version), once you drag and drop the new node into your models then new instances will use that updated version.

As you can see if need to change inputs/outputs then this is considered a new smart service as explained in the documentation forum.appian.com/.../Custom_Smart_Service_Plug-ins