A customer was trying to do apply multiple postcode filters using the 'start with' option but you only have the option to do '&' instead of 'Or'. They do have a work around which is to apply the postcode filter one at a time to add the contacts to their campaign activity but would be a lot easier if they could apply multiple filters at the same time for postcode.
We have currently only implemented AND rather than OR because it provides a simple and easily understandable user interface. We are going to look at providing a subset of OR functionality so that a filter for a specific field can have multiple variations e.g year is 2018 or year is 2017, but you won't be able to do "year is 2018 or year is 2017 or company type is Customer because it's not obvious how to interpret it.
To implement full OR functionality we would need to implement an "Advanced Filters" user interface providing the user an option to specify where the brackets go.