clippings

Some users have reported that the Clippings submenu on the browser context menu in Firefox would often disappear when moving the mouse to select a clipping or folder on the menu. This is caused by a bug in the Video DownloadHelper extension which causes problems with many context menus in Firefox. Upgrading Video DownloadHelper to the latest version will resolve the problem.
The font in the pasted clipping may not match the font formatting of the surrounding text inside a rich edit textbox (Firefox) or HTML message (Thunderbird). This happens if the text is formatted in a font other than the default (bug 20505).
On Mac OS X, digits 0-9 for shortcut keys do not work. Use letters (A-Z) only.
Shortcut key assignments are lost after migrating to the common data source.

You must download and install Clippings in both Firefox and Thunderbird if you want to use Clippings in both programs. Installing Clippings in one program will not install it in the other.
If, before migrating to the common Clippings data source, you have a large number of clippings and folders in the root Clippings folder, migrating from Firefox and Thunderbird may result in a larger number of clippings and folders in the common data source, resulting in a rather lengthy Clippings submenu in the host application's context menu. Consider organizing your clippings (deleting unneeded clippings from the root folder and moving clippings to folders) before running the migration utility.
Sometimes, if the common Clippings data source is enabled and you make changes to a clipping from Clippings Manager invoked from one host app and then switch to another instance of Clippings Manager from the other host app, the update from the first host app may not be reflected in Clippings Manager from the second host app. Use Options → Reload to update the display.
The Redo (a.k.a. "Undo Undo") function key in Clippings Manager has changed as of version 3.0; the function key is now F2.