The artist utilized the Volume Cube node to create the desired effect.
A VFX Artist known as "Late as usual" has unveiled a cool new project made in Blender. This time, the artist has set up a marvelous laser melting effect that can create molten holes in meshes. According to too the author, the effect was made using the new Volume Cube node, introduced with the recent Blender 3.3 update. What's more, the artist has also released the effect via Gumroad as an example file that demonstrates the uses of the new node. You can download it for free here.