Hi Jurjen,
Did you take a look in %DLC%\oeide\architect\eclipse\plugins\com.openedge.pdt.txt_10.1.2.00\runtime directory? maybe there is something there you could use to figure out what you need ...
There is always the brute-force-crazy way ... get the hWND handle of the Eclipse View that contains the file (I think there an function in oeideservice.p that does this), search for contained controls, get the hWND of the editor (which with some luck will be a RichTextBox) and then use SendMessage to scroll to the line. BTW you can always use Winspector (better than Spy++) to see whats going inside Eclipse.
And of course you can always ask Tech Support
HTH,
Ildefonzo