You can configure LibX bookmarklets to use either GET or POST. By default, LibX bookmarklets will use GET unless you enter a Bookmarklet Post Data Template under Optional Settings.
If you want the bookmarklet to use GET, you must specify the full URL template here. This template must include placeholders into which the user's search terms are inserted. The placeholders are denoted using a percent sign %, followed by an option code. Specifically, each occurrence of %option in the template is replaced with the value the user entered for %option. Option codes are listed in the search options menu. Possible choices for %option include all built-in search options (such as %Y for Keyword searches) and user-defined search options.
Example. To include google.com searches, use the URL template:
http://www.google.com/search?q=%Y
Make sure that the option with code Y is checked in the Options dialog. (Y is a built-in option which by default shows the label "Keyword", but you can change that in the Options dialog. Or, you can add your own option code, define your own option label, then use it here.)
Bookmarklets are very much similar to Firefox's Smart Keywords. In fact, if you follow the instructions on this page and create a smart keyword, you can convert it by copying the keyword's location (obtained from Bookmarks -> Organize Bookmarks -> Properties -> Location) here, then replace the %s in the URL with a search option such as %Y.
Important: If a bookmarklet should use POST, specify the only the URL here, do not include any %options, then specify the template that includes the options under Bookmarklet Post Data Template in Optional Settings.
The edition builder can automatically create bookmarklets from HTML pages containing forms. It will automatically populate either the URL template or the Post Data template, depending on the method used.