keyboard shortcut to extend a clip???

Move the playhead past the end of the selected clip - Shift X will extend the end of the selected clip to the playhead. If the clip is shorter than the position of the playhead, Shift-X will extend the clip to its end. PS - The selection of the clip should be either the left or right edge (as if you were clicking on an end to make a trim edit) and not the entire clip.

You can ripple the edit by dragging it. You can use Shift-X, the extend edit function. Put the playhead or skimmer farther than the extent of the clip and use the shortcut. The clip will only ripple to the extent of the available media.

I don't think so.

I just drag the ends out.

Do you have the edit selected that you want to extend? show a screen shot of what you're doing.

You are exactly on the right track - just select the trim edge of the clip you want to nudge, then type ',' or '.' to go one frame at a time - or hold the shift key down to move the end 10 frames at a time.