how to add a branch to a data tree

Basically i have a 2 data trees that contains points in the layout of straight panels, and i want to add one into the other starting from the next consecutive branch number from the first.

I tried insert items but because they're grafted to insert an index made the final points not merge as one

so the resulting branches should be 0,1,2,3,4,5... rather than the common branches, (0,1,2,3,4) merging with each other