Decoration Figures in JavaFX Editors
In the old SWT/GEF editors decoration figures where used to display
errors or warnings (model markers), e.g., due to canstraint checks like
weak causality etc.
This feature has to be implemented for the new JavaFX-based implementations.
(from redmine: issue id 3955, created on 2020-03-19, closed on 2020-03-31)