Hi, I'm on Houdini FX 20.0.547. When using Attribute Adjust Color with
Pattern Type set to "Line," the Start/End Position guide only shows as
a plain cross in the viewport. Clicking near it (instead of exactly on
it) resets the whole line instead of moving one point.

My teacher, on Houdini Indie 19.5.435, gets a full colored translate
gizmo (X/Y/Z arrows) when grabbing the same guide point, letting them
drag just one end without resetting the other.

I've already tried:
- Resetting preferences (Handles page, Dead Zones)
- Increasing Pick Distance and Handle Scale
- Confirmed regular Translate (T) works fine on other objects/Nulls

Is this a known version difference, or is there a setting I'm missing
to get the full gizmo on this guide?

Hello. It's probably a Python viewer state bug. It works properly on versions 19.5, 20.5, 21 and 22. If you're staying on v20, you can bypass the bug by creating your own handles. Go up one level and drop 2 Null sops beside your geometry node. Right click the Translate parameter of your first Null node and copy parameter. Go into attribadjustcolor node paste relative references on the Start Position parameter. Repeat this for the second Null node and End Position parameter.