Development tools for Zephyr on STM32Workbench for Zephyr: VS Code extension to set up, build, flash and debug Zephyr applications on STM32.Devicetree manager: browse, edit and visualize Zephyr devicetree, STM32CubeMX-like for Zephyr.
Sorry but there is no simulation implemented on System Workbench yet.
I don't know if it works but maybe you can used QEMU as processor emulator and upload your code on the emulator then to simulate.