Asset blocks are a wonderful tool. There is one limitation, however, in that only one object can be placed in a given asset block. I wanted to use three different kinds of trees altogether all over my route. I could have made three passes over the route with three different asset blocks. Here's a different way, for making just one pass over the route:
1) make n asset blocks, each with different objects;
2) move all those blocks over each other - no need to be precise, indeed better to offset just a bit;
3) now place the cursor near the edges of the overlaid blocks, and drag the mouse until the white circle covers a bit of the edges of all n overlaid blocks;
4) hit ctrl-c to pick up all those overlaid blocks at once;
5) move to wherever you want all those overlaid blocks, and hit ctrl-v - that places one over laid set under the cursor, allowing you to move the whole set about, and every time you click the left mouse button you get a new placement of the whole set.

Don't know if that works every time or not....