Your only venue to install Manjaro to a removable device is to do it manually.
There is several topics which related to installing on removable device - but your comment
make me say
There is no easy point and click installation to USB
- [root tip] [How To] Do a manual Manjaro installation
- GitHub - philmmanjaro/alma: Create Arch Linux based bootable USB drives
- [root tip] [How To] Manjaro-To-Go LXDE with persistance
- Install Arch Linux on a removable medium - ArchWiki
Feel free to visit my collection off notes relating to install Manjaro to USB - manually