I have one prop with two textures.  I make 9 duplicates and attach them all together to a dummy.  Now the dummy has 20 textures.  Is there a way to combine all these textures so that the main prop only has two textures shared between the 10 props?

Technically, if the material textures are still linked and "Affect all materials" is checked, then you still have 2 materials.
And any changes to one material replicated 10 times for each sub-prop.
It is a clutter in the materials list, which is annoying. But since the mesh is still separate, not much can be done inside iClone (iClone/3DX does not deal with mesh).
There is function in 3DX (Merge Identical), but it only works with newly imported .skp files.
So regardless, mesh joining and the *cleanup* has to be done outside of iClone suite in apps like Blender.

Thanks for the reply 4u2ges.  My understanding is that besides being annoying the long material list is a resource hog as well.  This is very irritating as I tend to put together my sets and advanced props inside Iclone.  Alas...

It would also be nice to have texture information available in the project tab similar to the triangle count data that is provided.

If the texture is linked for all materials, only one image is loaded into memory per texture slot and saved as project getting saved. So there is no impact at all....

But, I just discovered another horrible bug with iClone, where un-linking and linking texture back converts JPEG images into PNG.

In my testing I had 1 JPEG image 3.3 Mb in size applied to the Base Color of the iClone Cube.
I did replicate the cube 10 times, attached 9 cubes to the 10th and saved the project. The saved project size was around 4 Mb.
Which is good! Meaning the Base Color texture is referenced only once for all 10 cubes.

Next, I unlinked all Base Color textures and saved the project again. Suppose I should have the project size around 40 Mb. Right?
Wrong! The project size was over 130 Mb! I opened one of the textures in Photoshop from iClone and looked at the cache file in temp folder.
The very same file was now in PNG format and the size of it was 13 Mb. What a hell for?
I linked all textures again and saved the project. The size of it is now 14 Mb (instead of being original 4 Mb).

Imagine if you work with heavy loaded project and the texture size is growing as you link and unlink it, taking up valuable VRAM and disk space.

I already had 3 tickets opened in FT for similar matter. But you can't win optimization battle

Whoever is working on iClone 7.6 please make sure  this bug is taken care. Thank you