In auto symbol generation, you have to select Include Entire File option to include child subckt in library file. Here is a reference about Include Entire File
https://forum.qorvo.com/t/mov-subcircuit-component-check-pbkac/21458/2
In addition, TI DRV134 Pspice model file needs a modification to prevent it unintentionally end the netlist. Line#135 with .end command, this have to be removed. Here is .subckt netlist with that line comment.
DRV134.txt (4.0 KB)
And this is schematic which contain a functional DRV134 symbol
Balanced Mixer (Include Entire File).qsch (16.8 KB)