In most cases, you do not need to obtain the instance ID. If you are using a Show App button within a table, PerfectApps stores the child instance ID as a property of the button.
The instance ID of the current app instance can be found within the Special Fields or the Formula Editor. Both are accessed by behavior commands such as the Set Field command.
See also: Instance ID is Not the Instance Number
Return to: Linking Apps and Using Parent-Child Relationships, Designing an App