Plainrevs - you can... 1. show differences with the current version, 2. restore that revision, 3. pin it so it won't be deleted when the set max number of revisions is reached (as a snapshot, if you will), or 4. delete that revision.
Apply template - This plugin adds an apply-template button to the new Editor Toolbar to be shipped with release 5.1.12. Clicking on the beaker-shaped button applies the chosen template to the selection, by transcluding the template with the current tiddler argument set to the text currently selected.
Streams is a keyboard friendly way to write and easily divide your text into separate tiddlers while writing. Every time you want a new tiddler, just hit Enter. A new tiddler is created in the background and you can just continue writing.