File Selector tab in the Preferences dialog allows to define custom commands which are available in submenu of context menu in File Selector. By default this submenu contains single item which opens selected file with default application as configured in the system. Here you can add additional commands and set whether they should be available only for given file patterns or syntax highlighting languages.
Use New button to create new command, Delete button to delete selected command, and Up and Down to change relative order of the commands, they will appear in the menu in the same order as in this list.
The following entries set the command properties:
| 
 | Menu item label for this command. | 
| 
 | Shell command to execute when the menu item is activated. %fwill
    be replaced with full path of the selected file; if more than one file is selected then
    the command will be executed for each file one by one. Ifcommandcontains%Fand several files are selected then%Fwill be
    replaced with the space-separated list of paths of all selected files. If a single file
    is selected then%fand%Fbehave in the same way.
    Example:firefox %f,glade %F | 
| 
 | Semicolon-separated list of file patterns to define for which files this command
    is available, e.g. *.c;*.h. Use*if the command should
    be available for all files. | 
| 
 | Semicolon-separated list of mime types to define for which files this command
    is available, e.g. application/docbook+xml;application/x-glade. Leave it empty
    ifExtensionsentry defines whether the command should be enabled. | 
