I think that this example is only for the Leonardo and Pro Micro boards, that use ATmega32u4 chip, which has direct USB support. Other boards use a separate chip for handling USB, and thus can't act as a keyboard or mouse without some additional hacking.
However, since the software like Ardunio was made to work both with the development boards and the bare modules (and also a number of other devices that have ESP8266 inside them), they choose to refer to the pins by their GPIO numbers, not their Dxxx numbers. You can, however, refer to the pins by their Dxxx numbers if you choose the correct board definition from the boards menu. Then writing D6 will be the same as if you wrote 12.
The second source of confusion comes from the fact that the D1 board has some of the pins broken out several times, for convenience. So the pins D5, D6 and D7, which are used for the SPI peripheral, are also broken a second time to the SPI header, so that you can connect to them easier. However, they are still internally connected to the same pins, so you can't really use them for two different things at the same time.
Ey 7th Dwarf! thank you very much for your feedback.
I am actually using a software that reads a bmp file from a sd card, and does an interpretation of this to drive the led strips. There is a very good reason why I want this software to run in a central master board, and it is that I can easily have access to this board and modify its content, while the led strips that would be connected to the several D1 mini would be placed rather inaccessible, like for example hanging from trees.
I actually have the feeling that the first thing you proposed, that you also wouldnt recommend, could be a solution for my problem.
Since this is my first approach to use wemos and wifi, I have no idea where to start. if you have some experience and you can support me on my first steps, I really appreciate it!
btw. I can post only every 10 hours, until I get 3 "reputation" points. I would appreciate some!!!