L2 + R2 = third cross bar

[evilsohn]

...snip...
Unless you can very quickly and precisely tap R1 the exact number of times to shuffle to the bar you want.

You can change which skills You scroll through with R1 and wich are ignored in the options.
You can also change the rotation of this for weapon sheathed and drawn seperately.

You could put crossbars with porting, riding, and social emote stuff on Your weapon sheathed rota, while only having combat related stuff on Your weapon drawn rotation.
There is a good youtube video that instructs You how to do so, don't remember the link though, sorry.