Help needed with Military layouts

[NightFalcon650]

Goodevening,
First of all i love the work your putting or put into QGIS and your tutorials on Youtube. Hoping to see more of that :-D
I downloaded your layout for the 1:50000 (military UTM-MGRS system) from https://layout-hub.github.io/.

I tweaked them to what i needed, but still i'm missing one part and i don't have the knowlegde to get it done in a short time, therefore i'm hoping you could help me.
To make overlays i don't need the compleet grid system visibel but only a reference cross in the right upper en left lower corner, so i could lay it over a underlying map. A cross with the x and y number and the 100km letters. Locations are the red boxes.

How can i get this to work?