As of today, Mapton now supports UI scaling.

It’s available in the development branch and in the new snapshot.

Start mapton with an argument like this:

mapton --fontsize 24

or edit your $MAPTON_INSTALL_DIR/etc/mapton.conf like this:

default_options="--branding mapton -J-Xss2m -J-Dnetbeans.logger.console=true -J-ea --fontsize 24"

fontsize 12 equals scale 1.0, so 24 will double it.