Hi Roland,
The numbers in column 3 are character positions in the file being displayed in the next panel. When you click on the numbers, or keyup and keydown, the file text position will change accordingly. You can also edit the file text and save it with ctrl-S. This is an efficient way of making minor changes to multiple files.
In the leftmost panel you can list clusters of filepaths, separated by blank lines, and optionally do recursive searching on each filepath: -r. To select a cluster, click on the first entry of the cluster.
FindEd needs a cosmetic makeover, but I rely on it increasingly, especially for tracking symbols in o2 source code.
I run it JIT from source script, as it only takes a fraction of a second to be up and running.