Comment # 2 on bug 997028 from Oliver Kurz

Sure, more detailed description:

I am using a machine with a hard disk with overall capacity over 40 GB.
Using the graphical installer, on the partition proposal screen, select either
LVM or cryptlvm. Disable the "home" partition, keep the filesystem proposal for
"btrfs".

This yields a partitioning proposal with a volume group called "system". Within
the volume group a logical volume called "root" is created. The "root" LV is
created with a size of 40.0 GB even though there would be more space. I did not
change the default filesystem proposal "btrfs" so subvolumes are proposed.

To change the size of the LV I went into the expert installer and right-clicked
on the root LV, selected "resize", selected to use the maximum space,
confirmed. After the proposal was computed all btrfs subvolumes are lost from
the proposal.