I noticed that there is no direct link to the manual in the user interface and I think adding it would improve the usability.
For me I returned to using Duplicati after a 1-2 year break. When starting duplicati today I had to first go to the github page, find README and follow the link to the manual there. Googling probably would have been quicker. I think adding a link to the manual somewhere at the bottom of the page or at least in the about section (which was the second place that I checked) would be a nice improvement, especially for inexperienced users.