Merge Bones and their Weights (Vertex Groups)

Is there a way to merge 2 bones together including their weights, or copy the weights from 2 bones and paste them into a new bone (new vertex group)?

There are some 3D models that have too many bones or have redundant bones, and I want to reduce their numbers.

I wish to do this without using bone parenting/constraints.

Searching for a solution with Google only gives me results related to mirroring vertex weights.

You can merge one vertex group into another one by applying a Vertex Weight Mix modifier to mesh.
So, you can rename a vertex group to bone_top and merge the other one in it.

If you don’t care about vertices weights but just their belonging to a group, you can activate select one group of vertices and then, another one and eventually assign them all into a third group in edit mode or wieght paint mode.
It is a pity that we cannot select them by their weight.

Thank you, that worked.