When you look for example at panel TEN0041, the TPX Main Menu. Here you find four variables 'Z':
_Z:uentuser; PF:Z + <Z ¬z +
They are related to the list starting with .ZVARS located below the marker )INIT:
.ZVARS=(UENTSLCT UENTPJMP UENTLAB UENTWSTS)
The first Z is replaced with variable UENTSLCT, the second Z with UENTPJMP and so on - I marked the pairs of Z and the relating variable name with colors. The reason for using this ZVARS-list is that the names of the variables are longer than the values. The PF-key is only two bytes long but the variable name is UENTPJMP. This technique allows to keep the length of the fields as short as necessary.