You can save a procedure on the disk at any time. To do it, click on 'Edit' and and then on Procedures --> Save to disk as.
A saved procedure can be loaded on the Procedure Editor by clicking on Procedures --> Open from disk.
Once you load it on the editor, you can edit it like a regular procedure on the library. Please note that the name of the procedure is followed by a '+'. This convention marks the procedures that are not in the library. To add the procedure to the library (and remove the error that indicates that the procedure does not have a category), use the feature Procedures --> Add to library.
Once you add it to the library and assign a category, the procedure is saved on the repository of the instance in which you are connected: if you close and reopen it, it will not display the '+' again.