I have seen in the changelog there is a new feature called “user-led”.
But I couldn´t find any documentation about this, can anyone tell me what it does exactly?
Is it possible to align an antenna via the led?
Yes, in one of the next releases we will have such option. (aligning the antennas)
We will try to make some documentation.
Currently there is such options:
:led user-led=yes
:led user-led=no
And what can I do with it right now?
Just do a kind of disco inside the cpe enclosure? 
If you don’t need it for future signal monitoring, desolder the LED, and hook a solid state relay or other useful electronics up to it.