You can use the following Variables :
$path : Installation Path
$url : URL
$scriptname : Script Name
$backup_file : Web Directory
$error : Web URL
$backup_note : Backup Note
$sn : Site Name (Can be changed from Softaculous Admin panel -> Settings)
$user_name : User Name
$user_email : User Email

Note : You can use an IF for an Optional Variable in the following manner :
<if $VARIABLE_NAME>$VARIABLE_NAME</if>