Persist properties panel state across sessions

Is your feature request related to a problem? Please describe.

Currently, when you restart the Modeler, the layout state (e.g. groups are collapsed/expanded) got set to the initial state (e.g. all groups are collapsed). The only things we are currently persisting in the config.json are the width and the open state of the properties container.

"layout": {
  "propertiesPanel": {
    "open": true,
    "width": 250
  }
}

With the new properties panel architecture, we are theoretically able to listen for more specific layout changes as well (cf. https://github.com/bpmn-io/properties-panel-persist-layout-example/pull/1).

Proposed solution

Assuming that I as a user switch between contexts in order to compare or copy/paste:

• Ensure that properties panel open state is persisted across diagrams.
• View is restored on a best effort basis; if a section opened does not exist, open it
• Scroll position is restored on a best effort basis (i.e. open sections)
• Store the layout state regarding groups open state in the config.json and keep it across sessions. As an example, the next time I open the Modeler, the same groups should stay expanded.

Describe alternatives you’ve considered

• Instead of storing it globally, store it on a per-file / per-execution platform basis?
• This could be configurable via UI as well
• Not only the layout but also the ordering of groups could be something to be persisted

Additional context

• https://github.com/bpmn-io/properties-panel-persist-layout-example/pull/1

[nikku]

@christian-konrad @CatalinaMoisuc I propose that we pick this up as the next bigger topic in core editing. The proposed solution is to persist open sections across diagrams / potentially in the session; basically restore the properties-panel@0.x behavior. It has been been validated numerous times in a number of bug reports raised folks duplicating this bug.

The current situation is a huge UX blunder for everyone using the modeler as a power tool.

[CatalinaMoisuc]

Note from prio discussion with @christian-konrad today: we should consider both Modelers when drafting a solution for keeping the state. We want to be able to persist state also in the Web Modeler.