Confluence macro plugin for creating sequence diagrams from plain-text instructions. This plugin is simply a wrapper around Andrew Brampton's excellent js-sequence-diagrams, that enables it to be used directly in a Confluence page.
Start by creating/editing a page in Confluence, and inserting the macro either via the Macro Browser (under "visuals", or search for "Sequence Diagram"), or by simply typing {sequence-diagram.
See the js-sequence-diagrams page for notation examples.
The Macro browser allows you to specify the theme ("simple" or "hand"). You may insert multiple sequence diagrams on the same page, and each diagram can have a different theme.