@Allen Ah thanks for clarifying. I believe this should work the same for RNBO node as any other C++ node. You need to add these flags to your projects Extra Definitions:
NUM_HARDCODED_FX_MODS=4 //or however many slots you need
NUM_HARDCODED_POLY_FX_MODS=4
It is possibly you may need to first add that to HISE's extra pre processor definitions in projucer first and recompile HISE, then also add those to your project (so it works in the compiled plugin).
The documentation about this is a bit hard to find. There's also a forum post about it here.
Here is a spreadsheet of the different HISE flags you can use (it needs to merge this into the documentation somewhere).
Just for some extra context this is straight from the docs:
// number of modulation slots for Script FX
HISE_NUM_SCRIPTNODE_FX_MODS=0
// number of modulation slots for Polyphonic Script FX
HISE_NUM_POLYPHONIC_SCRIPTNODE_FX_MODS=0
// number of modulation slots for Scriptnode Synthesisers
HISE_NUM_SCRIPTNODE_SYNTH_MODS=2
// If you plan to compile the DSP network to a C++ node
// (which is possible with this node since HISE 5.0), you will
// also need to set the corresponding preprocessor variables
// for the hardcoded modules:
// number of modulation slots for Hardcoded FX modules
NUM_HARDCODED_FX_MODS=0
// number of modulation slots for Hardcoded Polyphonic FX
NUM_HARDCODED_POLY_FX_MODS=0
// number of modulation slots for Hardcoded Synthesiser
NUM_HARDCODED_SYNTH_MODS=2
