This is a request for a delete button at "WHM :: Main >> cPanel >> Reset a Mailman Password" that performs the this function:
This request is coming from two motivations
A) There can be mailing lists displayed by "Reset A Mailman Password" that belong to deleted accounts
B) With "Enable Mailman mailing lists" disabled in Tweak Settings, no UI at all was available to remove mailing lists for existing accounts.
Once the "delete list" option is available, it may make more sense to rename the page to "Manage Mailman Lists".