QUICK TIPS

Ctrl-Alt-R opens a root terminal.
Scripts are located at /usr/share/dxt2/3
(check they apply to your situation and edit as needed before running)
Activate weekly TRIM
Run installtrim from root terminal. Important: only for SSD installation. (Changes the scheduler to deadline).
Burn iso to flash
dd if=dxt3.iso of=/dev/sdx status=progress && sync
(where /dev/sdx is your target drive)

Use sync after every usb operation if you work with flash drives a lot).
Disable automatic login
Run sed -i "s/autologin-user=/#autologin-user=/g" /etc/lightdm/lightdm.conf from root terminal.
Refracta tools
Use Refracta Snapshot to create a snapshot of your system and restore it with Refracta Installer. If not already installed run installrefracta from root terminal.
Setup progress
To see what the install script is doing when "Running preseed..." press Ctrl-Alt-F4. If running in a VM just (right) Ctrl-F4.
Add swapfile
Run addswap from root terminal. Defaults to 2G.
(not compatible with btrfs - if you formatted your drive in btrfs use a swap partition instead)
Customising conky
nano ~/.conkyrc
(not from root terminal)
Exportiso
Does not work on Bullseye. Replaced by Refracta.
Setup Flatpak (DXT3)
Run setupflatpak from root terminal (once-off)
- this step is already complete in DXT2 - DXT3 is an offline installer and adding a  repo during offline installation is not possible, that I'm aware of).

Installing: Now you can just right-click on any flatpakref file and select "Install Flatpak". Note: the first time you install a Flatpak it will download all the base files needed for Flatpak to work properly, so the first one is a big one.
Background radio without wm (DXT3)
Open Menu > Multimedia > Radio Player and add/edit your favourite station. Enable "Autoplay on Startup" in settings. Leave the player on your station of choice. Then go to Menu > Session and Startup > Application Autostart and enable Background Radio. Reboot.
Customising hotcorners (DXT3)
nano ~/.local/share/hotcorners/hotcorner.conf
(not from root terminal)
Install Firefox latest
Run flatpak install flathub org.mozilla.firefox (after having setup flatpak) - at some point this will be integrated.
Replace grub boot image
Run cp yourimage.png /boot/grub/themes/dxt3/background.png from root terminal, in the same folder as yourimage.png.