When you add a column, you should then be able to click on that column and have the option to choose out of those visible in that column as to which can be viewed. For example, if you added Source to your columns and wanted to only see SCCM Probe or User or Workflow or a choice of more than one - like excel, you should be able to tick which options you want visible in your criteria for that column.
The search functionality in Freshservice is not very user friendly and does not allow you to conduct a thorough search. Often you have to export into a CSV and then work outside of Freshservice in order to gather the information that you need.