There is a huge problem with the Source Box
If you use it to add a source to multiple people in the tree, every time you edit that source for one of those multiple people, it puts the same edit on all of those people -- even if you add an Event Date. You should be able to edit a source on one person's page without it putting the same edit on anybody else's page just like you can if the source is NOT added through the Source Box. I have known this to be a problem for a long time. But I was recently helping someone who was changing the title each time she added the source in the Source Box to a new person -- ex. Birth Record for Mary Jones in _______ Parish Record, 1800-1850. So it changed the source title for everyone it was attached to to Birth Record for Mary Jones in _______ Parish Record, 1800-1850, no matter whose page it was on. In this case, it was siblings or cousins, so then what happened was because there were sources for Mary Jones on Abigail Matthews page, possible duplicates were showing up on Abigail Matthews page for Mary Jones! And we all know there are people who just merge all Possible Duplicates just because they are there. This is a huge problem. I was aware of it a long time ago, so I quite using the Source Box to attach sources. Instead I reattach it over and over manually as many times as necessary.
Before anyone assumes I don't know how to attach sources, try it. Add a source to your source box, attach it to a second person and edit the Event Date for that second person in his/her sources. Then go back to the first person you attached it to, or ALL the people you attached it to and you will see -- they all have the same Event Date. Which is fine if it's a birth record you are attaching to the child, father and mother. But when you find a page like this which has lots of births in my family, I could not add an Event Date to one without it putting the same Event Date on all of them.