You’ve mentioned a lot of different requirements in this post, but I’ll try to give you as much insight as possible.
Okey let’s just name that the org’s Agile tool is JIRA. And JIRA has a restful API. Is integrating JIRA and Visual Paradigm as simple as developing a VP plugin to interface with the JIRA API for the creation/update of user stories?
To answer this, integrating VP with Jira is quite simple and straight forward; as you’e mentioned, Jira has open APIs that you can use and VP has plugins which you can exploit. We use both within the organisation that I work for.
In the past, we had menu tools which automatically generate tasks when selecting a certain
IModelElement on a diagram. But we have enhanced our process as of late and now we use the scripting functionality VP provides. We run a series of different scripts at different intervals of the day, that automatically generates Jira tasks such as epic’s, tasks, sub-tasks etc. The purpose of this is that once our architects have modelled a solution within VP, these tasks are automatically generated and then assigned to our developers to work on.
Take a look at the following article about running scripts: Running Plug-in without starting Visual Paradigm
However, we don’t use the user stories functionality that VP provide so I haven’t really looked into automating this. As @ShelLuser has pointed out, it might be limited due to the diagram type. However, if you are able to add “tag” values or something similar to a IUserStory, you could store the automated Jira Id as a tagged value against the user story, and then have a script which can sync with Jira; to update the assignee, status etc.
This probably won’t answer all your questions, but I hope to opens a few new possibilities for you to look into.