Simulink real-time tunable structures

I'm working on building a model for a Simulink Real-Time Target (2019b). My hope was to include all of my parameters in a structure and make that structure tuneable. It appears that if I include a cell array of strings (which are used to configure some ip address values) the option for my structure to be tunable goes away.

Is there a way to allow my structure to still be tunable, even if all subfields may not be tunable at runtime?