I found that the file structure is different from other Add-on，It has the file which named *.sln. I tried to drag the folder to “My Commands”, it didn’t work.
By the way , what is the add-on shown on the screenshot?The icon just like a paint, on the panel of Robot programming .
.sln is a Visual Studio solution file so you probably have source code for some .NET plugin example.
It needs to be compiled with Visual Studio into a dll.
The icon is the icon of the Easy spot add-on if I am not mistaken: Easy Spot Add-On revisited
Sorry, it’s my mistake.The screenshot may be misleading.I meant the icon on the right of the Easy spot add-on.