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.
Even if CooCox isn't dead yet (I'd say it's dead but not buried) their forum is full of spammer bots and no genuine activity, so why would you want to register there given there are OpenSTM32 and GNU ARM Eclipse out there?