Godot haven't float containers, but you can use GridContainer
and dynamicly change it's colums
number through the script when the screen rotates. Like this:
func _ready():
get_tree().root.connect("size_changed", self, "_on_viewport_size_changed")
func _on_viewport_size_changed():
if get_tree().root.get_size().x > get_tree().root.get_size().y:
colums = 4
else:
colums = 2