Hello @numbqq,
In this link, there is a possibility of adding dual feature while there is no dual feature in Vim3. Can I add the mirror feature to the system by making any changes in the location(/usr/local/bin/hdmi.sh) you mentioned here ?
or,
You have activated this feature in Vim4. Where do you activate the Join Display feature in Settings > Display > Display Mode? Can I add a mirror feature by making changes to this file?