Hi Tim
Thank you for your message and great to hear that you are using
https://www.map.army.
The web application does only provide an Undo if you have deleted a symbol. You can find the following button in the bottom centre of the screen:

As all the layers are stored only locally in your browser, we do strongly recommend that you save your work from time to time (in the MilX Format). These saved layers can be reopened again in the Layer Manager:

Please do not hesitate to contact us should you have further questions on
https://www.map.army.
Best regards
Martin from the map.army team