I like CastleCMS's Add dialog, which is written in React, but until I (or someone else) figures out how to get that working fully in Plone, I wanted something quick and dirty. And, boy, is it dirty and it does not use React...
I need to do something a bit more in terms of feedback when you press Submit (or Enter) and it successfully creates the folder (or Page, etc.), like displaying a message “Folder created” then selecting the contents of the text field so you can just start typing the title of a new folder to add. Also, maybe when you close the modal it should automatically reload the page.
Multiple text fields could be displayed to let you enter more than one title at a time, but maybe that is not exactly the best way to enter multiple items. You might be thinking instead of pasting a bunch of titles from, say, a spreadsheet?