To find variables in the PLIDUMP output, you should compile your program with the MAP option. The MAP option will cause the compiler to add to the listing a table showing the offset within AUTOMATIC and STATIC storage of all level-1 variables that are AUTOMATIC or STATIC.
To find a variable that is an element in a structure, it is also useful if you compile your program with the AGGREGATE option. This option will cause the compiler to add to the listing a table showing the offsets of all the elements of all the structures in your program.