"Custom" partitioning for the installation destination may be unnecessary in many cases, so improve the GUI

[sjvudp]

How to file a helpful issue

The problem you're addressing (if any)

When you do not want to give the fully capacity of a device to Qubes OS when installing, one must use the "Custom" method when assigning the destination device, pre-creating most of the structure. And it's not easy to find the steps required (not part of the installation guide).
Also I had encountered a bug that the configuration wasn't accepted after needing several attempts to get the structure right: Installation would not begin, but after I had rebooted the installer, the same configuration was acceptable...

The solution you'd like

If the "Auto" proposal's partition sizes could be adjusted within reasonable size limits, there is no need for "Custom" installations in many cases.
Another case is adjusting some of the parameters of cryptsetup when creating the LUKS device.

The value to a user, and who that user might be

Avoiding the manual steps that are both, time-intensive, and error-prone, could improve the advanced user's experience avoiding unnecessary errors (when maing mistakes while executing manual commands), and saving time (by not having to execute all those steps manually (or repeatedly after an error))

Completion criteria checklist

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