Tested on LO 4.3.4 multi-lingual version.

Bug is independant of apps, aka whether Writer or Calc

How to reproduce the bug:
1/ Tools>Personalise>Toolbar and choose the "format" toolbar
2/ Check the components: "apply style", "font name", "size"
3/ Set the format toolbar vertically.
Observe that on clicking onto the
3.1 "font name" button you are prompted with a menu.
3.2 "apply style" button you have no menu
3.3 "font size" button nothing happens.

4/ Now set the format toolbar horizontally
and compare than when clicking onto the

4.1 "font name" button you have a drop down list
4.2 "apply style" button you have a drop down list
4.3 "font size" button you have a drop down list

EXPECTED BEHAVIOUR
Horizontal or vertical toolbar placement should NOT change the behaviour of the tools, therefore when placing the toolbar vertically, all 3 aforesaid buttons should have a drop down list.

Thanks