Where in your file-system is your PostScript file?
If inside of your Eclipse workspace (in one of your projects):
Setting breakpoints should work without problems.
If outside of your Eclipse workspace:
The Eclipse plugin API supports breakpoints only for resources inside the workspace.
Therefore it was not possible for me to offer PostScript breakpoints for files outside the workspace.
May be I should implement a warning about this restriction in a prominent place.
The right click on the side bar shows a context menu with Toggle Breakpoint grayed out. Double click on the side bar doesn't create a breakpoint.
Eclipse Platform Version: Neon.2 (4.6.2) Build id: M20161124-1400