I am a heavy user of X-Plane and always keep my NAV data current through a Navigraph subscription.
My question is about custom data for Navaids that we may want to add to the earth_nav.dat file for non-current navigational aids. Currently each new AIRAC cycle requires adding back to the file any manual entries that you've made. I'm wondering if there is a way to have a custom_nav.dat file that we could add these entries to once, and not have to keep modifying them back in each nav data cycle.
An example would be the now closed Kai Tak airport. This airport is still heavily used in the Sim community but the navigational aids no longer exist in the real-world navigational databases. So what we do is add the navigational aids manually to the earth_nav.dat file. Each AIRAC cycle overwrites this file and we need to add them back in manually again. If there was a custom_nav.dat file that was also read by X-Plane, it would allow us to add the entries a single time and not have to worry about it again.
Here is a custom scenery of Kai Tak along with an example of the navigational aids that are manually added with each AIRAC cycle.