Screenmodes are set according to EDID coming from the monitor. Customized settings are saved in SYS:Prefs/Presets/Monitors/yourmonitorname. You can copy and use this file on different systems and gfx cards as long as the gfx card is capable of specified resolution/refresh rate etc.

Screens (screen name combines name of the gfx and the screenmode) are "just" settings. It should be enough to go to the program settings and set it to use a specific, new screen).

Go to MorphOS Preferences -> Monitor. Add a new screenmode there and check if the image is correct in test mode.