I need to create the visualization of filling a glass regarding margins with the current value, but I can't find any tutorial on how to do that.
If you want a "gauge" visualization, Kibana already supports one. It can serve some of the same uses as a "glass filling" visualization.
As part of a Canvas dashboard you can use the revealImage function.
Otherwise, you can try to create a custom Vega visualization. I've never tried adding images to Vega, but it does support some advanced types like bullet charts
Perfect, thank you!