Folder view option for the selection of pdfs for new mindmap notebooks

When initially the pdf books are selected for new study mind map notebooks, there is no option to select pdfs in folder wise.

In that menu all the pdfs are listed without showing any folder that we made in the app. Therefore we have a trouble to find the pdf books that we need.

This is trouble when someone has to work with many lecture notes and many text books.

For example-

When I have to select books and lecture notes that i need for a anatomy lesson, i have to watch about 200 imported pdfs from beginning to end.

As well as when a lesson is done, some pdfs are no longer need for next lessons. But the user have to select the pdfs that they need searching among all old notes as well.

Please make an option to select pdfs in folder view/tree view in the next update.