Hi Kingsley,
As far as I know there is no support for a filter to search for custom content in a Datagrid 2.
One way that I can think you can solve this, is by creating a new attribute in which you can store the string or value that you want to search, and then utilize that Grid wide filtering for that attribute:
Alternatively you could opt for using a list view and see if that helps.
I hope that workaround helps you, regards!