You can use built in Configuration Editor and INI Editor to access and edit INI files. You can run ConfigurationEdit.exe that is in installation directory under SiCat folder to open Configuration Editor.

By defult this is found in below location;

"C:\Program Files\Bentley\OpenRail Overhead Line Designer CE 10.12\OpenRailOverheadLineDesigner\SiCat\ConfigurationEdit.exe"

Using configuration editor you can open any DAT file and access the contained INI file. First open a dat file using Open button. Then use INI files section to select required INI file and press Edit to open INI Editor. You can use INI editor to add or edit sections and entries.