highlighting a relation

How can I highlight all the elements of one realation together,
like I use to do at the past, just by clicking the relation?

I seems that this important option while editing a route was gone.

It seems you are talking about some Open Street Map editor. There are several, and you should specify which one you use (unless there is a consensus that I am not aware of).

I use JOSM, and you?

I use the built in editor, not any outside one