Due to a problem in the Quartus® Prime Pro Edition Software version 20.4 and earlier, the EDA Simulation Library Compiler GUI cannot recognize the Cadence Xcelium* Parallel Simulator tool's executable path even if the xmsim bin path is provided.
As a workaround, use the command line instead.
quartus_sh --simlib_comp -family <device family> -tool <EDA tools> -tool_path <path to simulation tool executable> -language <verilog/vhdl> -directory <output directory> -log <filename> -cmd_file <output_cmd file> -suppress_messages
This problem has been fixed beginning with the Quartus® Prime Pro Edition Software version 21.1.