As user during DMN model editing, I want to see validation errors on the model in case of wrong FEEL expression or invalid decision table.
I want to see this kind of errors in the decisions and at diagram level.

• As a user I want to run a validation test within the DMN editor, using the Validate toolbar action, to be able to identify elements within the graph or grids that have errors, so that I can resolve the issues.
• As a user when I save a file (and it is validated) I want to be informed if there are any validation errors, so that I'm aware that there are issues that need to be resolved.
• As a user when I test a rule in the Scenario tool and any scenarios fail due to a syntax errors within DMN, I need to be able to easily identify the portions of the DMN file with errors so that I can fix them.