I’ve tried to create a layer in Map Styler in Brave and then in Firefox as suggested by the forum. I click on a new layer. I added vector files as a source but am not sure what it means by “source-layer”.
The documents here
are not clear enough for me.
Vector tiles contain some layers that you need to translate to your layers.
So in the style you define that layer x has some color and the source of it is layer y from your vector tiles.
Map Styler is a tool to customize layers that are already available in our tiles. If you wish to add a layer with 3-rd party data then you need to edit the file manually. Docs here: https://developer.tomtom.com/maps-api/maps-api-documentation/map-style-specification