I only know what I have read regarding WinEQMOD which I have been using for over 10 years. The Custom Mount option provides a means of supplying parameters to replace the values the software uses based on the mount ID returned by the Skywatcher controller board. INDI/Eqmod must be using the same parameters in it's calculations for GoTos, slewing and tracking rates. The override values entered should be persistent between sessions and probably some indication on the main INDI/Eqmod dialog.
This is Win/EQMODs parameter entry dialog. You can select a mount/ratio from a list provided in a text .ini file or type in your own (if your brave!).
The title says it all. I have an HEQ5 which has a Belting Online belt drive kit giving a ration of 4:1 on both axes. As the driver stands, gotos etc are way out because of this and so my dream to controlling the mount with an RPi 4 is doomed. A tweak to the interface to allow the standard values to be overridden (and restored if possible!) would be excellent. In Windows/EQMOD this is achieved in the separate Toolkit app using a drop down list. of course there may be a way of achieving this already but no search I have devised has uncovered it (besides recompiling a custom version of the driver which is way beyond me).
Here's hoping and TIA,