Is it possible for OpenGL to be fed data from an external file, with the idea of building display lists at runtime?
Yes it’s possible but make the display list in your InitGL function.
I’m not sure why you would say to do it in the GL init function… I wrote a piece of modelling software which loads object files from the disk - I build the display lists once the data is loaded.
Build the display lists whenever you want, (within reason), you dont have to do it during your init function.
The usual restriction apply’s though : once created you cannot change them. (you can delete them and re-create, but you might as well use vertex arrays if you need to edit the data).