Click on a feature or path while holding down the Alt (Option) key. You should see a box with a couple of comments I’ve made about the feature.
Now click on the padlock on the bottom right corner. All going well, you should be asked to authenticate yourself with GitHub before given a dialog allowing you to change things. Save will close the dialog box; another Alt-click will bring it back with any changes added to the provenance records.
If GitHub authentication via the padlock doesn’t work, you will need to first go to https://flatmaps.celldl.org/login and authenticate there, before returning to https://flatmaps.celldl.org/viewer/ — once authenticated, the padlock symbol should open and close the input fields without further authentication.
Any feature can be annotated, including neuron paths, so this is a way to capture their provenance.