You mean you want to disable dynamic shadows? I’m pretty sure you can’t “disable” the baked ones. You can already turn off dynamic shadows in the details panel of your directional light (and skylight too if you have that).
Though, I’m not sure if the dynamic shadow casting can be changed at runtime or not.
If that doesn’t work, you could always try the Execute Console Command node. Here is a list of console commands.
If you set shadows to 0, I believe that turns them off.