Have you ever deleted multiple files in Explorer at once? Thunderbird works the same way.

Select the first message you want to delete. Then press and hold Shift and select the last message to be deleted. This selects all messages in between the first and the last one. By holding down Ctrl and click on a message you can select or de-select it individually. Then press Del to delete all selected messages.

I am looking for a tool to reconfigure so when clicked it will take all read emails to trash, or beyond.

eroomje,

please start a new topic for your question. https://support.mozilla.org/questions/new