Thank you! Your question prompted me to try some experimenting. I found an approach which is not perfect, but I think it beats transferring sources one at a time.
WIth the "new" FamilySearch, go to the "Sources" tab, then select "Open Details". Work down the list of sources and do two things: 1) if you don't want the item, close it with the big "X" at the top right in each box; 2) for items you do want, if the entry under "Citation" has a 'More' button, then click 'More'. NOTE: at this point you won't actually see anything more -- just a button that says "Less" -- that's ok.
Now use your mouse to select ALL of the text on the page (you can't start your selection with an active link, but you don't really want those anyway -- position to a piece of plain text). Then copy and paste the whole page either directly into the WikiTree narrative or to a work area. Finally, delete all of the extraneous text, retaining only the "Citations", and adding formatting. The complete citation is actually copied, even though you couldn't see it all to begin, and once you have saved it, the links work correctly.
This is lengthy to explain, but actually pretty easy to do.
You can also open the "indexed Information" using the associated "Show" button, and copy that information -- but of course the formatting won't transfer directly to WikiTree.