Installing, booting, logical problem shown by D-I

[yxcv@vienna.at]

I have a working machine with bookworm. Really nice one.
It happen to be booted from an  USB stick with DB12 SCSI10 for the moment

And I want it to bring Debian 12 from this stick SCSI10 to another stick, 
SCSI9!
which is prepared with db12-live now, but should be useable as quite normal 
bookworm on other machines.
Here is the table shown by debian-install and its partitionering
  

working machine  with /dev/nvmw0n1, part of RAID!
              1   MB     Freier Speicher
Nr.:1   536,9 MB  B  K  ESP
Nr.:2   998,6 GB           ext4
Nr.:3       1   GB       F  SWAP
           728  KB     Freier Speicher

SCSI9   (0.0.0)(sda)  126,6 GB  Disk 3,0 to be installed,  with DB12 
"live".iso now. 
                                  To be replaced by regular DB12.
SCSI10 (0.0.0)(sdd)      7,9 GB  Source disk with DB12.iso as the source and 
with D-I

Problem: The working machine cannot be changed, therefore SCSI10 is booted.
               And SCSI9 has to be partioned. 
But! Partioning tries to influence the working machine,  especially N r.:1, 
of course NR..3 too!
And! What does  B  K  ESP mean?

Thanks for reading up to here:-)
Ciao
Matthias