How to translate 债权 and 债权转让 into English?
the 國家教育研究院 (of taiwan, in traditional chinese) maintains a bilingual academic terms database.

http://terms.naer.edu.tw/download/

in 會計學, you may download the zipped excel file, 

http://terms.naer.edu.tw/download/101/Term_101.zip/

that you may find:

債權移轉　subrogation
債權，求償，索賠　claim

have fun :)