@ Amigaharry2 - Choose some files that fill that field/window and once you choose a file in that window it should make the window active and allow you to scroll through the available files.

I just clicked on the Audio (Categories) and then clicked on the first file, and the window then became active and allowed mouse-wheel scrolling. So, I hope that makes it work for you too.

I mentioned to Papiosaur some issues that are worthy of fixing, which he has already responded to me directly, but I mention here so other users know that these issues have been identified to him already, so they don't get duplicated unnecessarily.

They are in the GUI:

Hiden URL/Size - should be spelled - Hidden URL/Size (2 'd's) (a minor spelling point)
Ram should be CAPITALISED - to - RAM (Download archive to RAM:) as it is an abbreviated acronym (a minor point)