Desired delay in screen processing: After saving a particular transaction, the next transaction is automatically triggered. However, I would now like to delay the processing of the following transaction by two seconds or so. Is there a way to insert a delay/wait during the middle of a transaction process?

You can use the Wait= parameter of the Enter statement. Example:
Enter "/NLT01" wait="2000"
This will cause GuiXT to wait 2000 milliseconds before executing the /NLT01.  Maximum value is now 5000 milliseconds (i.e. five seconds). With versions prior to 2003 Q1 2, the maximum is 1000 milliseconds.