I wanted to add the solution to the “Email to end user regarding a Service Record” notification and found it was fairly easy

Using the available fields listed here:
https://documentation.sysaid.com/docs/custom-notification-form

added this line:

            #if(${isClosedSR}==true && ${Solution}&& ${Solution}!="" ) 
            ${Solution} 
            #end

Before:

             #if(${isClosedSR}==true && ${LinkToSurvey} && ${LinkToSurvey}!="" )
            Please rate our service: ${LinkToSurvey}
            #end

works great

John