Sketchup custom IFC property

Hello, sketchup/BIM noob here

This might be a long shot but, does anyone know how to add a custom IFC property? I want to create a custom property that showes MMI (model maturity index) when exported as an IFC and opened in solibri

I have tried with to do this with IFC manager, but i have not been successful.
Suggestions to other plug-ins are appreciated.

This is an example how it will look when opened in solibri:

Take a look at this

Those parameters are exported with IFC Manager

The plugin is here