The command line argument you are looking for is -always-load-scripts:
./qcad -h
Usage: ./qcad [Options] [Files to open]
-allow-multiple-instances Don’t try to avoid multiple instances from running
simultaneously.
-always-load-scripts Forces reloading of scripts when they are used.
This is mainly useful during script development,
to apply changes without restarting QCAD.
-app-id [ID] Set application ID. Multiple instances of the
same application (same ID) cannot run
simultaneously unless -allow-multiple-instances
is used.
-autostart [script file] Starts the given script file instead of the default
scripts/autostart.js. Note that with this option,
QCAD is not started but rather the application
implemented in the given script.
-config [path] Reads and stores settings to QCAD3.ini at the given
location instead of the default location.
-enable-script-debugger Enables the script debugger.
NOT recommended as this may cause unexpected
behavior when using QCAD.
-debug-action-order Print action oder information in menus
-exec [script file] [options] Executes the given script file directly
after staring QCAD. Options after the script
file are passed on to the script.
-gui-css-file [CSS file] Loads the specified CSS file.
-help Displays this help.
-locale [locale] Sets the locale to be used (overrides
the language set in the preferences).
E.g. ‘-locale de’ starts QCAD in German.
-no-gui Don’t use GUI. X11: don’t connect to X11 server.
-no-show Use but don’t display GUI.
-filter [filter] Opens the subsequent file(s) with the explicitly
given import filter.
-rescan Rescan scripts folder for new add-ons
-version Displays the application version.
-enable-xdata Enables XData (custom properties) support.
-quit Quits QCAD, for example after executing the
given script(s).
Mac OS X specific options:
-no-dock-icon Don’t show icon in dock. This should only be used
in combination with -no-gui.