if you prefer, you can implement all the state logic in C/C++ code. With Embedded Wizard you design the GUI components only. Both the C and GUI code can be mixed together. This is similar to how you exchange data between GUI and the remaining application code. You can invoke GUI methods from the C code. You can invoke C functions from the GUI code.
How you integrate GUI with your remaining aplication is described in Integrating with the device and Device Class and Device Driver.
Anyway, moving the logic to C will not simplify the implementation of your application. In any cases you will need to implement all the logic code. Doing this in C, however, will make this task much more difficult. You will nee to take care of additional aspects like handling of user events, state management of GUI components, screen transitions, ... These aspects are already handled internally by the functionality provided with Embedded Wizard.