Thanks! Although, in the browser, the FileDialog node doesn't allow opening user data; the proposal to solve this issue was from you, I think. Pixelorama, on the browser, opens the native file picker, rather than Godot's.
Oh yeah, you are correct. For the Web browser we use a modified version of this addon. https://github.com/Pukkah/HTML5-File-Exchange-for-Godot