It can definitely be done but the exact method will depend on which version of the smartthings app you are using as the rules engines are a little different.
FAQ: how to tell which version of the SmartThings mobile app that you have
That said, both versions have an official “smart light feature” and I believe both app versions have a “mirror” option, and that’s all you need. So you set up a virtual three-way where one switch mirrors the other.
To be honest, I can’t remember if you need to set up two mirrors (one starting from switch A and one starting from switch B) or not. But you definitely don’t need four automations, and that’s likely the problem.
But as long as you can turn them both on and off from the app now, mirroring should give you the virtual three-way you were looking for. 