I have several address lists configured on the firewall, I have just removed all IPs and all filter rules associated with this address list but it still shows up as an address list to add IPs too.

It is not causing any configuration issues, its just more of an OCD thing.

Is there a way to manually delete the address list?

save one /export and see if inside are present the list.

For force list to disappear, remove all rule where the list are used almost one time, and re-add.
If you remove the list/ip/port etc. fom one rule, if you try to re-add any later you find the field already populated with old value.

I removed all IPs and rules associated with the address list named "Blocked-IPs" and created a new address list named "Blacklist" I associated all the IP addresses from "Blocked-IPs" to "Blacklist" I even made sure to change the filter rules to reflect the "Blacklist" address list. However when I go to add a new IP to a address list the drop down still shows "Blocked-IPs" as one of the address lists

I am trying to get "Blocked-IPs" removed from the list