variable display properties not stored in project for hidden watchers

[heppg]

Had some trouble with variable properties: position on stage, display style, slider values are not stored to project when not visible. Current behavior is: adjust properties for variables. When storing project, some are visible, most are not visible. When project is reloaded, then the invisible variables loose properties and are displayed in default state (with label, no slider, slider values reset).

Expected: all variable display state is persisted in project.

Workaround: make all variables visible before storing.

This is (unfortunately) the same behavior as in legacy scratch 1.4.