Blank stencil for custom text!
You can use PrusaSlicer 2.6.0 feature to add your own text - I was missing the blank stencil, I created it to match with stencils I have already printed. Just edit the text, which have I already added.
Don't forget that the middle islands on the letters (for example triangle in letter A) will be separated from the stencil.
Happy printing and enjoy your coffee!