Start by typing in the nodes and edges in the text box to the right, then click "Draw Graph" to view your causal model. You can move nodes to where you want them, and scroll to zoom in/out. Once you're done, click the export button, and you can save the resulting png. If some parts of the exported image are cut off, you can increase the export padding. The code for this editor is available here.
Draw Graph Export to PNG Export Padding: top: bottom: left: right: reset padding