How can I edit HTML source during compose?

I often compose e-mails that contain multi-level bulleted or numbered lists, images, and other inserted items. Sometimes, Thunderbird fails to return me to the correct list level between paragraphs or breaks, or it crashes or deletes part of my message when inserting an image. I have found some workarounds, but it would be helpful to me if I could see the HTML code and manually edit it during compose, like I can with received messages (View > Message Source). I haven't yet found a way to do this. Alternatively, I could compose the message in Dreamweaver and copy it into my e-mail, but I might create some tags that are not supported by Thunderbird. Please suggest how I can edit the composed HTML before sending my message. Thanx, -Richard