In the SOAP Message feature set, we indicate variables using the following syntax: S{variable_name}. This allows us to pass a variable with the specified name from the SOAP message record to the web service function.
Reference:
Tutorial: Handling a SOAP Response in ServiceNow | John Andersen
ServiceNow SOAP - Cheat Sheet Cheat Sheet by bibingokuldas - Download ...

https://www.servicenow.com/community/it-service-management-forum/email-notification/m-p/695221 Reference:
When configuring the content of an Email Notification, the following syntax should be used to reference the properties of an event triggering the Notification:
event.<propertyname>.ThisisthecorrectsyntaxtoaccessthepropertiesoftheeventrecordthattriggeredtheEmailNotification,suchasevent.name,event.parm1,orevent.parm2.Forexample,{event.parm1} will display the value of the first parameter of the event.
The following syntaxes are not correct for referencing the properties of an event triggering the Notification:
current.<propertyname>.Thisisthesyntaxtoaccessthepropertiesofthecurrentrecordthatisassociatedwiththeevent,suchascurrent.number,current.shortd​escription,orcurrent.state.Forexample,{current.short_description} will display the short description of the current record.
${property name>.getDisplayValue()}. This is the syntax to access the display value of a property of the current record, such as current.state.getDisplayValue(), current.assigned_to.getDisplayValue(), or current.category.getDisplayValue(). For example, current.state.getDisplayValue() will display the state of the current record in a human-readable format, such as New, In Progress, or Closed.
${gs.<property name>}. This is the syntax to access the properties of the GlideSystem (gs) object, which provides methods for performing system operations, such as gs.now(), gs.getUserID(), or gs.getProperty(). For example, gs.now() will display the current date and time of the system. Reference: Email Notifications, Email Notification Variables