Blocker window is a simple Firewall interface. You can use it to enable or disable a blocker engine, but its main purpose is sort all blocker rules by priority - or assign a priority to them by sorting them out.
There could exist several Rules for a single connection. Blocker allows you to sort these rules by their priority. If a rule is higher in the list then its priority is higher and will be applied to a connection.
If you create two blocker rules for same filter and one of the rules will be set to
Ask and other to
Deny then the one which is higher in the list will be used and the other one (which is lower) will be omitted.