A proper 3D Bezier spline, with each point editable in the viewport. Support for loop. Useful for a lot of stuff, car racing games, traffic, all sorts of animations, to move or place objects on the path, or move a camera on the path etc.
The current alternatives are not scalable and hard to edit.
The Curved movement extension Details - GDevelop documentation requires hacky SVG set up and is very limited in use, mainly for screen size 2d levels.
Pandako’s 3D path tracer is far more usable, but you need to input each 3d point position value manually, from the viewport properties, and there is no easy way to copy paste the x y z values at once, so you need to copy-paste 3 times for a single point. Makes it quickly impractical for more than 20 points. Editing those afterwards is double the trouble.