I know it will be too late to add this to the next release, but perhaps add it to the to-do list:
1. Hide/Show - Added Files - those images that have been already taken from the ftp area and added to the db are not shown in the view. This will also hide those folders that are then "empty".
2. Hide/Show - Non added Files - same idea as 1, but its the flip side of the same equation.
Both of these would be pretty easy to do as we already know which have been added :-)
Now as a reason for this.. think of a gallery with 4,000+ images, and your adding more to various places... it becomes a management nightmare to add new ones...
The "file filter" to me would be handy as I move entire blocks of folders over, or added data, and that includes files that are not image related, so they show up in the lists of files to "add" like a thumbs.db file or text documents. Another pretty simple addition (I think) a mask in the config, and then a check during the building of the "add files" page... etc...
I can live with the ftp files staying, although some how I do think it would be a cleaner implementation if the fftp area was just a "holding" area and the end result of the files were moved into the album area. Perhaps some day IF I can ever find time, I'll play in the php as well. something about kids makes that doubtful currently.
Take Care,
Quentin