Hi, Arkhon! Right-click on the name of the custom property in the Properties tab, and there should be an
"Enable Property Networking" option in the context menu. The property name should turn orange to indicate it is networked. Don't forget that the object itself must also have networking enabled.
Thank you, I realized it didn't show up because I've made the Object a Template before I tried that.
I had to Deinstance it first to see the option available.