Custom Table/Matrix

[PlacidFury]

I'm totally new to Deneb/Vega in Power BI, and am struggling a bit.
My goal is to create a table/matrix which displays the data I want in the format I want, which I can't accomplish with the standard table or matrix visualizations.
I'm having trouble finding a good tutorial that shows me how to do this. I've found a couple that have helped a bit, but I'm still quite a ways from my goal.
Does anybody have any advice on this, or links to tutorials I'm not able to find?
Thanks!