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.
Try right-clicking on the Project in the Project Explorer and select Index->Rebuild. Sometimes there's nothig wrong with the code, but Eclipse says there is because its Index is messed up.