Blender had some SDF nodes in 3.6alpha, but they disappeared after the release. These nodes were so useful. Just a few days ago, I found the names of SDF in the Python API（Blender 4.2 / 4.3 / 4.4）. I was confused because they were not in the menu, so I tried to find them with Python, and it worked!
There are 10 nodes here
I made an addon, add a menu to the geometry node.
I also used these nodes to make some cool Node Assets
In a build of main branch, volumes nodes in development are hidden behind an experimental tag.
You have to check New Volumes Nodes option under New Features panel of Experimental tab of Preferences window, in a 4.5 alpha build, to reveal them in menus.
Yes, but alpha verion only for play or test, in my job, i have to used release verison.
You played with 3.6 alpha. The fact, that they are mentioned in Python API, does not mean that such node is officially supported in official release.
The development of the nodes is simply not finished.
With official 3.6 or 4.4, you have to limit yourself to Volume nodes present in menus, if you want to avoid unexpected issues.
You are right. Those nodes are not official. People should know that.
But for the official Blender, I believe the other parts are safe. So all my risk lies in those nodes. It will be safer than the alpha version. Hahaha~
Anyway, thanks for what you said. 
Hi! Could you share the node tree for your addon?
thank you.
