Multi Channel Setup in HSM Edit

[alundRQ4XG]

I'm using Fusion to make code for a Star swiss lathe--separate programs for main and sub spindle. I happened upon the "Multi Channel" view in HSM Edit and would like to use it to check my wait/sync codes. I'm having some difficulty trying to configure my Multi Channel settings to adjust which codes are recognized as wait/sync codes. The Multi channel mode called "Fanuc (M2xx)" is close to what I need (my sync codes are M200-M899), but doesn't include some key M-codes that act as sync codes.

When I open the settings, I can switch the "Multi channel mode" to User defined, but the checkbox for "Synchronization using channel numbers" is not visible and appears to be toggled on--which completely breaks the functionality for me as my wait/sync codes do not specify channel numbers (just a 2-head machine). In the Help User Guide screen for Multi Channel settings it shows this checkbox as visible... How do I get this visible?