Everything for managing the URL cache. HTML mode accumulates a list of the URLs you use in your HREFs, SRCs etc., and saves the list across invocations of Alpha so it can help you to insert new URL attributes rapidly.
Clean Up... - After a while the URL cache can get very large and you may want to remove some URLs you do not need. You will be presented with a dialog box, as shown below, with a checkbox for each URL in your cache. Uncheck the ones you want to remove. Click "Uncheck all" to, guess what, uncheck all checkboxes. If there are more URLs in your cache than fit the window, there is a button "More" to take you to the next ones, and a button "Back" to go back.
Clear - Removes all URLs from your cache.
Import... - Scans a file and imports all URLs found to the URL cache.
Export... - Exports all URLs in the cache to a file for later use.
If you create several files with URLs and want to move the URLs between them, simply open the files and cut and paste.
Add Folder... - Adds the names of all files in a folder to the URL cache. You can optionally add a path before the file name. For example, if you have a folder 'pics' with images, you might want to add 'pics/file.gif' to the cache rather than only 'file.gif'.
Add Selection - Adds the current selection to the URL cache.
Add Clipboard - Adds the clipboard to the URL cache.