Actually, you can do it as follows : https://forums.steinberg.net/t/split-stereo-track-into-two-mono-tracks/899810/2
I’m aware that the Artist version doesn’t give as much options as the Pro one, but the essential here, is the Export as setting, which should be set as Split channels.
Additionaly, and if you want both the L & R channels to appear as two mono audio tracks in your project, use, in the After Export setting, the Create Audio track option : it will allow you to get these from your original stereo one directly in your project.