In the link you posted, the last comment gives the command to rename the container. Does podman rename fedora-toolbox-38 fedora-toolbox-39
not solve the immediate problem?
I think long-term though, you want to recreate your toolbox using the Fedora 39 image since just renaming it will still keep it based on the Fedora 38 image.
Toolbox, being based on Podman and container technology, isn’t really designed for long-term use. In the container world, they are created and destroyed once their purpose is done, and updates are done by recreating the container using an updated image.
FWIW, since your data should reside outside the Toolbox container (e.g. in your Home directory), you should be able to create a F39 Toolbox using the F39 image, add your packages, and basically be back in business with an updated environment.
I have a script that I run which customizes the Toolbox environment how I like it. It allows me to create/destroy the Toolboxes at will and recreates my custom environment every time.
You can do something similar. Run the following in your current Toolbox to get a list of your personally-installed packages and writes them to a file “packages.list”:
dnf repoquery --userinstalled --disableexcludes=all --queryformat "%{name}" > packages.list
Take a look at the list and customize as you desire. Admittedly, the list that this creates is not really accurate (it includes stuff that I didn’t install myself and comes with the default Toolbox). If anyone knows a better command, please share. So you should delete stuff from the list until you only have the list of packages you want in your new Toolboxes. Good news is, you only need to create this list once. If ever you want your future Toolboxes to have a different package, just add it to the list manually.
Then I have a simple script that sets up my Toolbox, which I run from within every new Toolbox I create:
#! /bin/bash
# Install my list of packages
sudo dnf -y install --skip-broken $(cat packages.list)
# Set up my doas config
sudo sed -i 's/permit :wheel/permit nopass :wheel/g' /etc/doas.conf
# Default dnf to Yes
echo "defaultyes=True" | doas tee -a /etc/dnf/dnf.conf
...