goxel.xyz
Goxel is an open-source 3D voxel editor for desktop and mobile, created by Guillaume Chereau. It uses sparse matrices so scene size is unrestricted, supports layers, runs on Windows, Mac, Linux, iOS and Android, and exports to formats including MagicaVoxel, Qubicle, glTF2, obj, ply and build engine. The desktop version is free.