Would be awesome to have an option to drag fields from one Flexible Content to another. Inside parent FCs or nested FCs, without any dependencies of the FC location.
I’m afraid that’s not possible at the moment.
If you want, kindly open a new ticket so your request can be passed to the plugin author. You can open a new ticket here: https://support.advancedcustomfields.com/new-ticket. Also, please don’t forget to explain the request again.