I don't know whether there are tools that can do that. Definitely not from MS.
If you want to write your own tool that will do that, you will have to take a look at CMI interfaces.
Otherwise, relatively easy way to merge SLX would be merging them in XML formats. Basically save your SLX as XML in TD, open both in
notepad and copy/paste the list of components from one to another. You can always go back to SLX format when the merge is complete.
This however doesn't cover scenarios where you have the same components included in to both projects. If those components don't
allow multiple instances, I don't know how TD will react to these collisions at the SLX loading time. (you let us know please after
you play with it)