Issue with libraries - moving files to a newly created library

If you select images in a library, this can apparently only be done one by one. There seems to be no way to select several files at once. With a large number of files, this can be very tedious.

It should be possible to select multiple files at once using the keyboard (select first and last file while holding down the Shift key, which would select all files in between).
It is also not possible to deselect several files at once. There is no button to deselect selected files.

If you want to move more than 50 images from one library to another, this does not work, no images are moved.
Tests performed: 41 images can be moved at once, 51 images cannot be moved at once.
I therefore assume that the limit is 50 images.
Actually there should be no limit for the number of files to be moved.