Make legend visible to users at all times

[tmdobson]

The legend showing which colours denote which elements is located by scrolling down below the entire tag list and is not visible when manipulating the models. Is it possible to make it visible to users as they work with the models?

[lagoan]

Can this issue be combined with Issue #6? This way we could have a window showing the information like:

Total nodes : 100
P nodes : 50 [P colour block]
Narration nodes (narrator:man): 25 [Narration arg:man colour block]
Narration nodes (narrator:woman): 25 [Narration arg:woman colour block]