Blender add-on: BIS v. 1.6.4.

Two new modes were introduced to work separately, one for materials (easier to use) and the second – for node groups (for advanced shader making). In the “Material” mode, the entire material is stored and loaded. In the “NodeGroups” mode, everything works without changes, a separate node group is saved and loaded for the convenience of creating complex shaders.
In the “NodeGroup” mode uploaded node group adds to the current open node group instead of the node tree root as before.
The experimental mode can be enabled/disabled in the add-on preferences.