Haven’t used DataSmith so can’t help you with material indexing.
1 - how to add actors to the array of
static meshes
Actors are actors and static meshes are static meshes. They are 2 separate things. You can group each into their respective arrays in many ways. One of them is demonstrated in your screenshot. You can use Tags, it’s very powerful when used right. You can use Get All Actors Of Class, you can use Get All Components.
2 - when pressing x … the objects
changed materials randomly between a
and b , not all of them together to a
then by pressing x into b
You’re using FlipFlop so you’re changing every second one of them, and the last one you change twice since your completed executes 1 extra time. Drop the FlipFlop node.
3 - how to pick which element to
change for every object …
You could try Getting the material out of the static mesh, check what it is and then decide using a condition.