Can multiple grounding electrode conductors be placed on the same ground lug?
That lug can’t be double-tapped.
Large wires can generally never be double tapped.
Check the labeling on your panel for the list of sizes allowed for double or triple tapping on which lugs. Don’t expect wires larger than #10 to be permitted.
You must obey panel labeling and instructions NEC 110.3B.
If your wire can’t reach, feel free to use the vacant screw hole just to the right of the main lugs to mount a lug e.g. a double lug.  Electrical supply houses stock those.  It is probably a #10-32 screw.
You can also drill your own holes, but must be -32 thread pitch or finer. Nobody ever got fired for using 10-32.