looking for resources for Voxel Editor development

I am an experirenced opengl dev making 3D tools (but not games) for a while now, and my potential next project is a voxel editor similar to Voxedit or the editor in sandbox.game.

I am looking for resources how to make similar rendering editor, when I searched the net and even youtube tutorials, I can see there are tutorials but most of them are solely focused on terrain generation and rendering and all of them are not even complete, missing the part of the actual edit of the voxels like adding, delete, ALL of them.

Do you guys know …