How to add a new material slot

To add a new slot to the material slots for an object:

1. We can use the operator object.material_slot_add

Calling this operator creates a new material slot for all selected objects:

But this operator, like all of operators, is context sensitive an may be inconvenience when using.

2. We can also append a new material slot to an object directly to its “data.materials” collection.

Execute the following:

to add a new empty material slot to the active object.

If we need to create a slot and immediately assign a material to it, we can pass the required material in the parameter: