Hello
Currently there is no way to do this without duplicating the information, which we don't want to do.
So how did they get the other languages there?
Well, for instance, it looks like the information on Appendix:Proto-Indo-European/kʷetwóres for Celtic is the same as the corresponding information on Appendix:Proto-Celtic/kʷetwares.
I'd also check the rest of them; perhaps it would be good to not list the descendants of the proto-words for each PIE word, so that this doesn't happen again.
Also, someone who is also in this conversation said that I could add descendants to pages if they were missing, so could you see if my recent edit to Appendix:Proto-Germanic/fedwōr is sufficient? I don't want to do any more until I'm told that it's good enough. I can also provide the sources, if needed.
The point is that keeping the same information in two places risks one or the other getting out of synch with the other if there are additions, deletions or corrections. Click on the link to Appendix:Proto-Germanic/fedwōr, and if there are any missing descendants of the Proto-Germanic term, add them to that page. Just remember to add them in the right place in the list, and be careful about adding hypothetical forms that aren't worthy of their own entries in the appendices (there's an anonymous user who keeps adding Gothic terms that seemed to be made up by extrapolating from other languages, for instance).
Oh, that makes sense. Thank you, I'll keep that in mind.