Managing and Clean-up of Large library

I am taking over control of our company’s shared library and part of that effort involves cleaning up the library as it stands currently. I am aware that I will need to create a new library due to the inability to switch library owners easily, but I want to see if there are ways to help maintain the library going forward to avoid the issues we have with the current library. We have between 30 and 40 individuals with whom the library is shared and who are able to add references.

In its current form, our All References library contains >40,000 references, but this is due to a large number of duplications. The references that we do use/want comprise just above 11,000. In the new copy of the library I will be removing the duplicates, but I want to know if there is a good way to help avoid this happening going forward, besides constant monitoring for duplicates (such as running a check 1x/week for duplicates). We are not able to easily just delete the duplicates as we do not know which version(s) of a reference have been cited in any of our documents. So for the new library, I know you can see when a reference is added, but in a shared library, is there any way to see who added a reference? As you need to have an account in order to use EndNote as I understand, shouldn’t there be metadata for the account responsible for adding a new reference to a library? And if so, how is that accessed?