But just try swapping the currently recorded upgrade slots in the marksman file. If I understand correctly, everything should work. That is, the first upgrade of the third level will appear in the hiring window, and all other properties in the chain will not disappear.
I did as you wrote, and it turned out like this =)

Well, never mind, the previous version is quite good. There is quick access to level 1 archers, quick access to level 2 crossbowmen, and quick access to level 3 snipers. And the rest can be quickly upgraded in the city menu.
Added 11 minutes later
@Waterfall_13
In the PerParticleFog parameter, change false to true, and if the color component is not embedded in the particle, then the color will be read from the texture!

Unfortunately, it didn't work. The orange glow around the Blue Dragon looks out of place((( I guess I'll have to repaint it red (crimson) sometime in the future. So that the colors blend and look more natural.