Thanks to ocratato over at fedoraforum who had the simple solution of omitting the %u or %U and including a "-new-tab -url" for the first url (I hadn't included it before the second url) as well as any other urls. It just won't work with out it being present.
Noob Alert. Just joined hoping someone can help with creating a Desktop Entry to launch a new Firefox instance with multiple tabs. The -new-window part is easy but I can't find anything about multiple tabs.
If I do something like "Exec=firefox %U -new-window url1 url2"
The new window...