Custom Control on Paint node?

I'm trying to learn about custom controls in Fusion. I've attempted a dozen times to add a custom control to a Paint node and I cannot for the life of me get it to show up in the inspector.

- Add a Paint node.
- Right-click => Edit Controls
- Add a Number control, on the "User" page, with a SliderControl input.
- Close the control editor.

The "User" page appears in the inspector, but it's empty.

I've restarted Resolve, created a new project, created new Fusion comps. Same thing.

I can create a custom control on a Background node using the same approach and it works.

Am I missing something or is this broken?

I'm using Resolve Studio 19.1.4 Build 11 (the latest afaik).

Paint is a weird tool. Its controls aren't actually a tool control panel--they're modifier controls promoted to the tool interface. If you add a User Control, save the comp, close it, then reopen it, you'll see your control. But as soon as you start a new stroke modifier, the control will vanish again. I'd say this qualifies as a bug, and you should send it to Support