Custom MIME Type in Drag And Drop from QtWebEngine to Another App

[enterit]

Good morning,

Could anyone please tell if custom MIME types are supported in drag and drop from HTML in QtWebEngine?
I see them working properly when I implement drag and drop within the web-page. But I cannot get any custom MIME type payload when I drop to an external app (e.g. to Chrome).
Drag and drop of custom MIME type from one instance of QtWebEngine to another also does not work.
Drag and drop of custom MIME type from Chrome to QtWebEngine does not work either.

Is this a setting in WebEngine maybe? Or implementation limits?

I know that Chrome registers "Chromium Web Custom MIME Data Format" clipboard format in Windows and Linux, and that's what it uses for custom MIME types.
https://github.com/scheib/chromium/blob/d2338b606d6536d20975a601c197d3e2ee3cec0e/ui/base/clipboard/clipboard_win.cc#L394

Drag and drop of custom MIME types between two Chrome instances works, but drag and drop of the same payload between two instances of web pages loaded in different QtWebEngine processes does not work :/

If you have any idea how that could be fixed, it would be helpful.

Thanks,
Sergey