When Dynamics NAV 2016 was launched, Extensions were introduced as the new way to build Add-Ons. At that time, Extensions had too many restrictions, so developers were playing around with them, but only the brave actually started developing real Extensions implementations.
With NAV 2017, the number of restrictions have significantly decreased. Now the Extensions Marketplace (App Source) is growing at a rapid pace.
Following 1ClickFactory‘s vision, all companies will someday run on the latest version(s) of their software(s), 1ClickFactory‘s NAV developers commenced several Extension development projects to make it easier to upgrade Add-Ons. Through this work, a couple of peculiarities surfaced that you may want to make note of for your own Extensions development.