CSS for pagetree in lef sidebar

I want to use the pagetree macro instead of pagetree2 in the left sidebar (because pagetree2 lacks the sorting options of pagetree).

However, when used within the LSB, pagetree looks extremely ugly:

It should look look somewhat different (less space between the entries, smaller font etc):

 I suppose this is because of the style sheet of the left sidebar. As I did not change any style sheets in confluence before and do not know what I am doing (or have to do): Can anyone help me with this?