The mortar pit model works with the HM-38, as you can see in the trending image on the front page. Clone the mortar entity's "holdable_ext" and change "holdable" from "hold_large_gun" to "hold_mortar". You can do that for the light artillery guns as well. If you then also modify their weapons as I described above, they should be fully functional.
Edit: You also need to set "enable_in_building" to True for the barrage abilities.
Thx, Planet Smasher.
Thx for your help, the 120mm mortar finally fits in the middle. But, those abilities are still not able to active.
I have changed "enable_in_building" to True for the barrage abilities. To be more specific, When I am trying to active the mortar ability, it will start cooldown(the icon will turn yellow), but no actual action will be done, and because of this. The cooldown bar will maintain at the beginning. Could you please tell me how to fix it?
Edit, the mortar in the trench will not autofire at long range( close range yes).How do I suppose to change it?( I have added an ability to increase mortar performance when they are in garrison which including increase weapon range.)