Performance: On-demand lazy-loading source selector

It's a performance solution, but, in my opinion, a bad thing for UX.
The idea is still great, may be we can find something to solve UX.

UX issue:
It's a button, we are not used to have a button in a form to display a select list / other options to configure switch a field. If i saw this button, i will don't know why it's here and what is its purpose. It's not intuitive.

Proposal:
1/ May be we could add some things with this button so we understand it's a default source and we can change it. May be adding an arrow inside the button, at right like a select list does ?
2/ Be more verbose, with text AND a button : <span>Current source : URL</span><button>Change source</button>

I like goz's second idea and I think this could also work when nothing has been configured yet:

Props

• URL: Data from field (field_link) Change source for URL
• Color: -None- Change source for Color

We would have to define a way to display a "summary" of the existing settings but this would be way more effective for performances because we would only need to load forms on demand. The downside is still usability because it's one more click in an UI that already needs a lot.

Thanks both for your feedbacks :)

We would have to define a way to display a "summary" of the existing settings but this would be way more effective for performances

We have this now ✨ [2.0.x] Add PluginSettingsInterface::settingsSummary() Active

I like proposal #2 by @goz.

It would improve performance by reducing unnecessary load and avoiding the need to build the dropdown each time, which also helps users notice that there are more options for selection.