Talking about a desktop application now, not mobile or web.
Is it any widget in Flutter that will allow, for example, drag a folder, drop it in the application UI, and the app will read for example the path to that file or folder?
I have been reading about Draggable and DragTarget in Flutter, but i do think they are used for that purpose.
NOTE: it might not exist a widget for that purpose, so a strategy on how to do that in Flutter will also be appreciated.
Assuming you're talking about dragging from outside the application, it's not currently supported; Flutter #30719 would be the issue to watch/upvote.
Depending on the specific platform you might be able to implement it with a plugin in the short term (if you are familiar with native development on that platform), but that would likely be more work than contributing an implementation to Flutter itself.