Object Merging or hierarchy (feature request)?

[gpwood]

Hello,

I have a use case where plot objects exist in two parts (one a negative one positive). I'd like to "merge" each part into a single object so it appears as one item in the "objects" panel (rather than two). Is this possible?

So an example of this would be to take the six plots here: https://k3d-jupyter.org/reference/factory.marching_cubes.html#levels and merge all the hearts into one object and all the toruses into another, so that in the panel it displays only two objects rather than 6.