Setting generics/parameters in Synopsys Synplify
Go to the menu Options > Configure VHDL Compiler. This menu has an Extract Generics button which will identify the generics and add them to the form, so you can fill in the values. Here is a screenshot.
You can still use the power of Tcl, again, as we recommend:
set_option -hdl_param -set nbits 4
set_option -hdl_param -set maxcount 10