I opened C:\Program Files\SlickEditV19.0.0 x64 Beta5\macros\menu.e
Then tool->FileDifference.
Set file1 to the Menu.e buffer
Set file2 to C:\users\joe\downloads\menu.e
Diff.
In the right-side pane (downloads\menu.e), right click and select EditFile.
The dialog closes and Slick now has a buffer "C:\Program"