Use labelled bracket notation. This app will build the tree as you type and will attempt to close any brackets that you may be missing. Use Copy tree to paste the tree into a document, or Copy link to share it. To save it as a file, right-click the tree and choose "Save image as", or turn on Download SVG in Options for a file that stays sharp at any size. For more information, including on how to draw movement lines, visit the wiki.
This is a fork of mshang's Syntax Tree Generator. The forked code can be found at github.com/codylewis/syntree.