It sounds like you had some properties that were non-default on your layers that were interfering, but if you have default parameters on your layers Z-fill and invert then it's the quick and easy way to create a canvas where the text are pockets instead of islands when creating a new project from scratch. I'd suggest trying it again and make sure everything is set properly because it's important to have an understanding how/why things work the way they do.
- Canvas Z-Fill to top of canvas
- Layer's Z-Fill to bottom (default for new layers)
- Layer's Invert disabled (default for new layers)
- Layer's Remove Bottom disabled (default for new layers)
- Layer's Blend mode set to Subtractive
The text-layers are "white on black" for their heightmaps and all that needs to happen is they are subtractively combined with a canvas that has a Z-fill to the top of the canvas. You could also use the Difference blending mode but it can be a little less intuitive when manipulating layers with different Z origins and Z sizes, but it will be functionally the same if your canvas Z-fill is to the top of your canvas and your layers occupy the full depth or height of your canvas (Z origin is at bottom of canvas and Z size is same as canvas).
I'm wrapping up a fix and updating the User Guide and aim to have v1.58b out by the end of the day :)
- Charlie