Refactor to remove global `mrWidgetData` object

The following discussion from !15114 (merged) should be addressed:

• @winh started a discussion: (+3 comments)

  To be honest, I find this way of passing data to the frontend a little weird. Given that you only followed the existing pattern here, I consider it out of scope to change here.

  If you agree, we can create a follow-up issue to further discuss. Otherwise feel free to just ignore this comment. 😃