"I edited a spreadsheet in my wiki, but the changes weren't remembered ?"

I am guessing you uploaded the spreadsheet using Zwiki's upload file feature, then you clicked on the link to open it up in your spreadsheet program. This downloads a local copy of the spreadsheet (to some temporary directory) and your changes will only be saved locally (and will be lost pretty soon.)

What you could do is re-upload the temporary spreadsheet file - after saving it, edit the wiki page again, click browse and find the temporary file (in /tmp on unix systems), and re-upload it using the same id as the existing upload. I think it will replace the old copy.

That is tedious, so it may be better to configure and use the ExternalEditor product. Once your spreadsheet is uploaded, visit a url like http://your/wikifolder/externalEdit_/spreadsheet.xls (add the link to your wiki page to save typing). With luck, EE's zopeedit helper will start the spreadsheet program and this time when you save, the changes will be saved directly to the server.

That's still a bit tedious if you're working with many spreadsheet files. Another option is to open your wiki folder using a ftp or webdav-capable file manager (details depend on your platform) and then just open/edit/save the file directly.