I think I've run into a bug in 7.2.0 Standard that defeats the Export Libraries feature much of the time. The main symptom is that during the export process a dialog pops up with "[Somefile.scr], Line [n] The Standard edition of EAGLE can't perform the requested action! You can't create layer 4". See attached image.
The root of the problem is that the Export function does not create the output libraries directly, instead it creates a script which it runs to create new libraries "in" the one or more new libraries. This generated script includes instructions to create in the new library a <layers> table corresponding to that in the source library.
Many source libraries contain a layers table with a complete set of entries. The generated script for these libraries contains instructions to generate a corresponding table in the new libraries which includes script steps like:
Layer 1 Top;
Layer 2 Route2;
Layer 3 Route3;
Layer 4 Route4; <---- Oooops
Standard is not allowed to execute the Layer 4 command, because it's restricted to 4 layers total, including Layer 16 which is Bottom. So Eagle prevents the script from continuing. This despite the fact that the libraries in question don't actually do anything on the offending layers, other than just declaring and naming them.
It turns out that such a script can be repaired in a text editor by deleting all the lines that declare layers other then 1,2,3,16. It's necessary to run the repaired script from the Schematic editor (or possibly the PCB editor), but not the library editor, as running the script there just causes the library editor to close.
Have I overlooked some way in which this all is intended behavior, or is this a bug? If it's a bug, how do I report it most effectively?