Debian 12 Graphical install - unwanted Guided partitioning

[Roger Price]

I have to replace a dead SSD and re-install Debian 12.  I use Graphical Install 
with manual partitioning of the disks so that I can specify mount points for my 
existing RAID partitions on spinning disks.  During the specification of my new 
partitions I made a mistake, and selected "Go Back" to correct the error. This 
took me to "Guided Partitioning" which does not allow me to specify mount points 
for RAID partitions.

Is there some way within the Graphical Install to get back to manual 
partitioning without having to start again from scratch?  I backed up to 
re-specifying the root password, but that was not sufficient.

Roger