At the top of Identify, click Debugger > Setup debugger...
You can change it in the Default Waveform Viewer pull-down menu in the Waveform tab.

Also, please set the environment variables for the waveform viewer.
Quote: "Make sure that the selected simulator is installed on your machine and that the path to the executable is set by your $PATH environment variable."
https://ww1.microchip.com/downloads/aemDocuments/documents/FPGA/ProductDocuments/UserGuides/sw-ugs/Synopsys+Identify+RTL+S2021.09M+Debugger+User+Guide.pdf#page=86