How can I invert my surface masks?

This behavior has changed as of Lightform Creator version 2.1.4 released on March 31, 2021

Paths in a surface now have selectable boolean operations - This makes it easy to combine paths in flexible ways, such as subtracting one path from another. Pro-tip: When merging surfaces, keep track of each path by selecting "Auto-Name Paths" to have the path name reflect the surface name. Read more about these operations here.