GodAtum,
The fix pages do not accept coordinates, which is how your ETP(s) will be displayed in the OFP.
What you can do is go to the end of your active route and enter a throwaway fix (I enter my home airport). Next, below your throwaway fix, enter the ETP coordinates in standard format. Then, just delete your throwaway fix and LEAVE the route discontinuity boxes displayed.
Your ETP will show as a white fix in the ND, but you will not get ETA or estimated fuel overhead figures for it. It’s good for situational awareness.
We also always enter the ETOPS entry and exit coordinates in a similar manner, as these are quite important (especially the entry one).
Best regards,
Mariano