The process to add several materials to a single object is really confusing and not intuitive.
Suppose we have 3 materials (MA:Green, MA:Red, MA:Blue) and a cube without any material assigned to it yet. We want
all three materials to be assigned to this cube.
In this context, the following 2 button panels are relevant:
1) Shading / Materials button / Links and Pipelines.
2) Editing / Links and Materials.
And that's precisely the connection between the two that's confusing.
Say that in Links and Pipelines the cube is already assigned the MA:Green. We now go to the Links and Material window
to add a new material index. If we do so, a new material MA:Green.001 is created. We must go back to Links and Pipelines
to select the proper material (MA:Red).
The problems are:
a) Doing a simple operation (adding an existing material to an existing object, in a new index) requires some back and
forth between two different button windows.
b) When creating a new Material index for the current object, one would have expected to be able to select the material
straight away (maybe with a pulldown menu with existing materials to select).
c) Instead a new, unwanted material is created, cluttering further the interface.