I have managed to show a progress bar when the form is submitted.
Pending tec...

I have managed to show a progress bar when the form is submitted.

Pending technical debts:

• Currently, the ajax command libraries are loaded inside WidgetBase. I believe they should be loaded as part of DisplayBase, or somewhere else in the stack.
• Similarly, I found that the current ajax submit callback can be easily removed, or can be moved to somewhere else in the stack.

Pending work:

• It works if you have selected an existing media entity, but breaks when a new entity is selected.
• Implement progress status callback.