This should be built on top of the feel popup stable release #419.
What should we do?
We need to enable both the local FEEL popup, but also the web modeler popup, such that they are able to react to external value changes like undo/redo, or any other programmatic changes to the properties panel.
Why should we do it?
This is a long standing issue with the popup panel, and we'd like to rectify it. Especially now that we invest into things like the FEEL playground in the web modeler.