It depends on what you want to achieve.
If you need that for notifications – you can use custom script to format message("%[ScriptName]" macro). Example:

And script ("CustomScript" in script library):

if ($event->id == 17) { // SYS_THRESHOLD_REACHED, adjust to real event
	if ($event->parameters[1] == "System.Memory.Physical.Used") { // $1 is "Parameter name" for SYS_THRESHOLD_REACHED
		total = GetDCIValueByName($node, "System.Memory.Physical.Total");
		return "Too much physical memory used (" . $event->parameters[4] . "), total: (" . total . ")"; // $4 is "Actual value"
	}
}
return $event->message;

This is just an example, you need to adjust it to match your setup (e.g. if this action is used only for specific event in EPP, you can omit $event->id check the script).

A bit more about using scripts in actions: https://www.netxms.org/forum/configuration/actions-parameter/msg3178/#msg3178

If you need event with both values (e.g. for further processing), you can post custom event from transformation or threshold script (https://wiki.netxms.org/wiki/NXSL:PostEvent)