That was what drew me to antiX and then to its big brother MX Linux – the ability to put the OS with persistence on a flash drive and use it on any of my computers. Whichever of the computers I had available, I’d boot the USB drive and continue working from wherever I had left off. It was a huge plus when I was distro-hopping as I could move my work to any computer without actually locking in the install. All of that changed when I decided to stay with Manjaro, installing it on each of my machines. I no longer needed that portability.
There is a way, supposedly, to do this install of Manjaro on a USB drive. It’s not necessarily for the faint of heart (and I don’t think it’s the same as what @linux-aarhus referenced in his post just now). Here is the post I found if you want to experiment and have the time to spare (of course you have the time – you’re retired!!!)