superpose multi-Volume

Hello,
I need to show multi-volume in the same render. But, I can’t superpose them.
How can I do that, please?

See this example:

Note that multi-volume rendering still has limitations, such as shading is not available, and there are also a few small bugs, but they will be probably resolved within a year. If you need it sooner then you may consider contributing with development work or funding.