Make a caption n a copper layer in eagle
TL:DR
Same problem , different tool, 4 ways

Adapt to your tool


Polygon method
Bitmap Import 
DXF Import 
Custom TrueType Font


Polygon method    

Home | Fill - a filled polygonal shape with any number of vertices

Home | Solid Region - a simple filled rectangular shape

Home | Polygon Pour - a filled polygonal shape that will repour around other objects ... Like text

https://www.element14.com/community/docs/DOC-89106/l/adding-logos-to-your-pcb-layout

You may find better answer already in Eagle forums...  no more time here

You are pretty good and much better than I ...
 "if you read all the internet"