・Is it possible to get the FOC sample code in any way other than generating it in the workbench? (For example, is there a library on the Cube IDE, Workbench, or ST site that can reference other FOC code?) )
No i don't think so. The generated code is in .c files, if you want to edit the existing FOC code you can do it.
・After "Generate Program" in the workbench, an error occurs when importing to the Cube IDE and debugging. Is there something missing or wrong with the procedure?
You have to build the project and see if there are no compilation errors, if no errors then your code generation is proper.