TL;DR: Undo/Redo and isDirty is broken. The issue is on the VSCode side and this functionality won’t be available in Dev Preview.
We are already in contact with the Microsoft team about the issue. We expect that this issue will be solved hopefully on the next VSCode release, in about a month from now.
As soon as we confirm that this problem is fixed on VScode Master as a potential alternative, we might suggest users use VSCode Insiders with a new kogito tooling release.