Hello @BrianS7168 ,
I agree and apologize this is not easier to accomplish. We have work being done to make things like this easier, including a new Contacts Redesign that we are currently Beta testing. When the redesign is fully launched, we will have the ability to manage Tags in bulk and it should be a bit easier to target contacts on multiple lists.
In the meantime there isn't a great workaround for finding who those contacts are without using Excel, however if the end goal is to remove List A from Lists B and C, you can go into List A > check off all the names > Manage Lists > Remove from Lists and this will give you the option to choose which lists you want to remove the selected contacts from (Lists B and C in your case). You won't know WHO it affected but you'll know that there is definitely no one in List A that are also in Lists B or C anymore.
If this does not help, you can also give a call to our Support Team and they are more than happy to help clean out lists with you or provide real time workarounds that may suit your specific needs! Hopefully when the redesign is out, this will no longer be a pain point. Thank you again for the feedback!
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