I set up Net Class 4 in DipTrace (width 0.15, min 0.1, max 0.15), but when I place a trace it defaults back and I can’t change it manually. Why is the max showing as 3, and how can I assign default nets to other net classes? I’m on Windows 11 with the latest DipTrace Standard update.

When you select the Route Manual tool, the Routing panel appears on the left, where you can choose a Net Class.
If you are routing a new net, you can select its Net Class from the dropdown list.
If the net already exists, it already has its own Net Class — therefore, when you select another Net Class, it will automatically change back to the one already assigned to that net at the start of routing.
You can change the Net Class in two ways:
1. From the main menu: Route / Net Classes
2. From the context menu of the net — Net Properties.