There is a solution but the texture must be in livery (texture and line in description.lua) or in cockpit mod (if you are speaking about helmet reflection in both cockpit) for others don't know.
Always working for me, I know it's in french but I made a tuto in french website maybe this will help you https://www.checksix-forums.com/viewtopic.php?p=1652841#p1652841
Open the track file with a Zip or RAR soft, you have a "options" file, open it with Notepad++, find SARPS change true to false or 1 to 0, don't remember and I am on m'y phone.
And in the last update Release/Beta 2.5.6.61.527.3 we can see this in change log
NS 430: Manual brightness cannot be adjusted - Fixed (Caution - do not set to zero, as NS-430 screen will become unusable).
And no update in manual ..........
Please, please, please, Shift+F10 for labels and LCtrl+Y twice for statusbar (Maj+F10 pour les étiquettes et LCtrl+Y deux fois pour la barre d'état en bas)
Un p'tit partage ???
Long time ago I asked question to find the texture of screen when it is off, just wanted to make a mod with a simple black screen, no reply and never fond this texture
Installé au mauvais endroit, ça s'installe dans C:\Utilisateurs\...\Parties enregistrées (Saved Games)\DCS version\Mods\tech. Depuis le temps que c'est dit et répété sur tous les forums ......
Ce ne sont que des non pilotables (AI only) et pour l'icône sur la page d'accueil tous les mods issus de le communauté n'en ont pas forcément, c'est un choix du moddeur