Are you using Parcels?
If you code is in a parcel or parcels, just use the Parcel Browser and sleect the parclel and pick either the "Save" or "File Out As" options. Both produce a text file of the Smalltalk code that can be easily imported into another Smalltalk image
If you are not using Parcels, you can still use the "File Out As" option in the System Browser to export a Category, a Class, or even just a Method as text that can be published