editable accelerators no more working in xfce4-terminal after GTK+3 migration

After last update on my Fedora release 24 installation, even after I select "enable editable accelerators" in the xfce4-appearance-settings window, I am no longer able to remove the Alt+ shortcuts in xfce4-terminal which are used by default to switch tabs. This interferes strongly with irssi which uses them to switch windows. Would it be possible to either re-enable the edition mode or provide another way of setting those shortcuts?