Waiting for data indication on main inputs

I noticed when _nodes inside a flow are waiting for data_, they have a purple indication. But when the _main inputs are waiting for data_, there is no indication. This makes it hard to understand what's going on in the flow...

I think there should be a similar indication on the main inputs as well 🙏

Start by locating the UI component that renders the main inputs and compare it with the existing purple waiting-for-data indication on nodes. The work is done when main inputs visibly show a similar indication while waiting for data and the flow state is easier to understand.

Written by the indexing model from the issue text.