I`ve set habitable planets to abundant (or how is it called) so I should have a mass of habitable planets.
Only in Dark Avatar or the base game. The max amount of habitable planets has been drastically reduced in Twilight of the Arnor. From what I recall, this was done to reduce the memory usage and allow a bigger map size (Immense).
Still, you should have at least one habitable planet per star system. So, are you absolutely certain you've set the habitability to abundant, and not just the number of planets in general? It's a common mistake. Happens to all of us.
Or is there a way to alter configuration files to have more habitable planets?
The data for the map generation (number of stars/planets/habitable planets, etc.) is hardcoded. Without access to the source code, it's not possible to change any of this.