When I start a new project and create the nodes they work fine but then after a while working when I go to adjust the smoke object, there is no red box with handles…
I use a dual screen custom desktop and I just tried switching to another preset like animation and the handles came back. Then when I switched back to my custom desktop the handles remained.
nice! it's worth logging the bug, via the support menu above. Houdini has had quite a few problems with dual screens and the bugs get fixed in the long term.