Custom properties for user widgets without eez-flow

[devcarbon-com]

Is your feature request related to a problem? Please describe.
When using LVGL without eez-flow, there does not seem to be a way to add custom properties. As a specific example where this is a problem is when trying to make a user-widget where you would like to reuse the structure and style, but want an individual instance to have unique properties, labels, etc.

In my current case, I'm making a scrollable list of settings, and currently there is not a way to use custom labels, events, etc. per each.

Describe the solution you'd like
I would like to be able to "raise" a property from a descendant widget to the top-level (user-widget) property panel. Ideally, with a custom name.

Going back to the setting-item custom widget as an example, this would allow me to design this layout:

+-------------------------------------------+
|  [setting-label]   spacer   toggle-switch |
+-------------------------------------------+

And assign the label & custom event per user-widget.

Describe alternatives you've considered

• Copy-paste widget (Tedious to modify every instance later while adjusting UI)
• Modifying the generated code (Not hard to do, but you loose ability to further edit the UI without having to manually redo your code edits)
• Allowing for custom-code to be inserted in the UI (Not as nice, but would be (probably?) an easy feature to implement in the meanwhile. Similar to above approach, but gets us closer to not having to redo the code changes every time.)

Additional context

• I'm programming for a rp2040 board, and it seems it doesn't have the resources to run eez-flow.