would you mind to reveal us what you are trying to do?
Creating a template that could be used for easy screen captures. The screen captures wouldn't typically be saved to disk, but pasted directly into the template. In worst case scenarios, where I didn't create a PDF or some other output that would make the screen prints available in their original capture, and Scribus wasn't available, I was hoping I could use the Base64 (however, not sure it is Base64) in the sla file to easily recreate the image. I can do this with LibreOffice's Draw when the file is saved as a Flat XML ODF Drawing (.fodg).
Further testing: I exported an svg from Scribus and was able to recreate the image from the Base64.
Images shouldn't - generally - be pasted into a Scribus document. Pasted images are for specialised purposes only. Use image frames instead.
When I copy and go to Edit | Paste, Paste is not enabled, so I used the Insert | Insert Image Frame.
Thank you for the replies.
(Modified post to correct some errors.)