I have created a model library (class package containing several other class packages). It currently exists in two versions -- one in a single .mo file and the other in a directory structure using the within keyword. Both versions load and execute properly in OMEdit. The single file version can be edited and saved. The multi-file version cannot be saved. A save command generates several messages of the form

Expected the package to have within ; but got within <packagename>

Is this a known limitation of OMEdit? If not, I believe I can provide a simple demonstration file.