Click in the open space to add a node: left-click for a “basic” one, right-click for an “important” one.
Drag from one node to another to add an edge.
Ctrl-drag a node to move the graph layout.
Shift-click a node to change its label.
Click a node or an edge to select it.
Operations on selected nodes / edges
When a node is selected: R toggles reflexivity, Delete removes the node.
When an edge is selected: L(eft), R(ight), B(oth) change direction, Delete removes the edge.
Save / load functionality
Save SVG saves the graph as an SVG format file which you can then further edit using appropriate graphics software, e.g. InkScape.
Dump JSON dumps a JSON representation of the graph to the JSON Input / Output textarea. Save this into a text file if you want to resume working on your graph at some point in the future.
Load JSON takes the output of a previous Dump JSON operation that you’ve pasted back into the JSON Input / Output textarea and recreates the corresponding graph, so that you can continue where you’ve left off.