Question:

How do I filter for debtors that's amounts are not allocated?

Answer:

Please apply the following filter below.

C_CB does not equal 0 or C_CB <> 0.0

The system will now only display the debtors amounts that are not allocated or unallocated. 

In other words those that display in Red. 

Note [!]:

The same filter can also be applied to creditors, but will entail who you owe money.