I have a medium size email list (~4500 for one business) and wanted to apply granular unsubscribe to those potential customers so that they were less likely to fully unsubscribe.
I created the following lists "All Contacts" "Monthly" "Weekly" "Events" and "Sales/ Discounts", so that folks can have better control about the frequency with which they are contacted.
Taking my current contacts within Zenler and adding them to this list involved manually checking a box at the top of the page for just 15 email subscribers at a time -- 317 times total. It took me a half hour to do this task that would have taken 3 minutes on Mailchimp.
You can see a bit of what it took me to do in this Loom video: