Hi,

I sent you an e-mail yesterday, but I will post it also here for other users.

You can take inspiration from the folder selector which is used e.g. in the Media library module in Tools section when you want to copy some folders. you can find the code here \CMSModules\MediaLibrary\Controls\MediaLibrary\FolderActions\SelectFolder.ascx.cs. It is designed for current media library, so you will need to modify it to use the media library name e.g. from a drop down list, where the user will select the media library and according to this selection the folder structure will be shown.

Best Regards,
Juraj Ondrus