Where should I put an administration page that should only be used once?
I am creating a plugin that will index all used HTML tags in your posts, so you can cleanup posts if you change themes and want to replace old incorrect <font>
tags with headers or other semantic markup. When you install this plugin it should scan your old posts once to fill up the index (custom taxonomy). I don’t want to do this on plugin installation because it might take a long time if you have many posts, and thus a separate page with an AJAX-approach to transform batches of posts might be better.
It’s probably nitpicking, but should I put this extra page in the menu (under Tools?) and just leave it there, or should a use a trick to only display it when needed? Via a link in the plugin actions, or maybe a DB setting that you can use to hide the menu item? The plugin should remain installed (because it updates on post inserts and edits), and maybe sometimes you want a rescan (if you did a bulk change via the database).
As plugin users, does it bother you to have menu options that you almost never use?
Putting it under Tools seems reasonable to me. Hiding it after a certain action might cause confusion.
I agree with Scribu.
I use Regenerate Thumbnails ( http://wordpress.org/extend/plugins/regenerate-thumbnails/ ), and it is found under tools. It kind of a run once and forget about it plugin.