[Adoby]

You have to do it in steps.

First get the contents inside () and before the - to #Customfield1:

Search title for: .*\((.*)-.*\)
Replace with: \1
Destination field: #Customfield1

This will put aa in #Customfield1.

Then remove the paranthesis:

Search title for: (.*)\(.*\)
Replace with: \1
Destination field: Title