At the moment it's not possible to auto merge links from linkgrabber to downloadlist that have same package name
You might wanna try to use the eventscripter, see
https://board.jdownloader.org/showthread.php?t=70525
You can also ask mgpai for help as he is our eventscript master!
he might also be able to help you to check links for changes as there is no support for subscribing to channel and check for changes