In my opinion, the Configuration - Edit/View dialog is difficult to work with. Here I list my objections, my suggestions and a screen mockup.
My objections to the current dialog
It is confusing that when you select one of the radio buttons, it looks like the options are changing because the keys behind the options change.
The default for F3 is Internal Viewer with selected files. It's more intuitive to list that option first.
Associations and Default external viewer look like sub-options of the radio button External Viewer. They are however independent options. It is not intuitive to set options for a radio button option that is not selected.
In my opinion is more logical to list the default external viewer first and the Associations button to set extension specific external viewers second.
"Configure internal viewer..." should not be aligned with options for External Viewer. It looks like a sub-option of External Viewer which it isn't.
My suggestions
Use a combo box and labels instead of radio buttons to set the hotkeys for the lister functions.
List "Internal Viewer with selected files" first
Use a separate label for the External viewer settings.
List the Default viewer first, Associations second.
Move the "Configure internal viewer..." button to the left.
IMHO in this case "Configure internal viewer..." button also could be put on the top of all elements:)
This may be the first option among the specified!
Because the first action which you want to do in this section - is exactly the (re)configuration of the internal Lister tool.
