View #17 on GitHub to know more details
Currently custom report allows the user to use the format function to change the display format of individual column. Their are a set of pre-defined functions at this point. Need a option to allow the user to add their own function and use it to format the fields.
Following are the issues in implementing this functionality:
Till the time this feature is implemented, you can always raise a new issue to implement/add a particular format function as a inbuild option which would be quick and easy to implement. But if you are requesting for a new format function please be clear with all the required details / screenshot to understand your requirements clearly.
As this feature can be achieved using Report Builder, this is no more in need. Hence closing this issue.