You could use Expand values operation in the DataManager and use "(" as the separator value. Operation will result in the field with values you need, and the field with rejects you can delete in the next step.
We are looking into adding "*" value in the Search/Replace operation, where asterisk can represent any number or combination of characters. In this case you would search for "(*)" and replace with null.
Note - my suggestions will work when replacing the cell values, but not if you wish to rename the fields that contain the names in brackets. That you would do in the Field Organiser.
Note that Omniscope supports Regex (Regular Expressions) within text processing formulae...this is able to cope with almost any such text parsing and re-writing problem, but is much less accessible to non-developers than the methods outlined above. This has been posted as an idea to define * wildcard text substrings and replace them systematically within one or more fields, without having to write a RegEx expression.