This is to ensure users don't get confused with the fact there's
more checkboxes to check in the modal until they can continue.
Depending on viewport size, checkboxes can be hidden but it's not
obvious that the area is scrollable.
See #8651Closes#8651
Fixes#6411
- fix the order of buttons and the Skip button transparent background
- don't let the subHeaderItem eat vertical space when it's not visible
- layout/margins/spacing/linespacing fixes
Pascal Precht
Michał Cieślak
Stefan
MishkaRogachev
Lukáš Tinkl
Patryk Osmaczko
Alexandra Betouni