[DMN Designer] Multiple DRDs interactions review

The current multiple DRDs support in the editor follows the guided lines provided on this UX team guidelines:

• on this document: https://docs.google.com/document/d/14pnw6QUTj5BsUJyz4uP_ozLLkYBvCYGXd1VIaK6jFHQ/edit
• and, on this mockup: https://marvelapp.com/prototype/jb9i419/screen/62691972 and

However, during the development, and the PR review, some corner case scenarios emerged.

This JIRA comprehends UX output for those points. The following feedbacks will guide this investigation::

• User can't create DRD before an element is added to the diagram (source: https://github.com/kiegroup/kie-wb-common/pull/3379#issuecomment-689614893)

• The icon for DRD-related actions is the sign used commonly for "Share" (source comment: https://github.com/kiegroup/kie-wb-common/pull/3379#issuecomment-689614893)

• There's no clear indication of what DRD or DRG I am currently seeing (other than checking the decision components present on canvas)

• It would be nice if the currently selected node on canvas would be highlighted in the Decision Navigator too.

• The "Share" icon doesn't provide enough clues for users that it's related to a DRD

• Consider adding a button on the Decision Graph to create a new DRD, which would not require to click on the "Share" icon on the shapes

• Add a visual clue, when users are editing the DRG (maybe similar to the visual clue users already have when they are editing a DRD)

Besides these scenarios raised by Jan. I'm starting thinking about behaviors like this:

• I have a DRG with 3 nodes: Input, Decision, BKM
• I create DRD with my Input and my Decision
• If I come back to the DRG and delete the Input, we're also deleting it from the DRD, because the DRG represents the global context. Should we really delete nodes from the subset?