Heh, lines 1000 and 1016.. Were those just an example? I expanded the limit to 1024 lines in the last release, but didn't expect such a need
But going back to the question. There is no way to loop a small group of lines, inside a pattern, but you have several help tools:
First, the key F7, which will play from the line the cursor is, onwards. This does not loop, but at least you will be able to start exactly where you want.
Also, you can use the keys 4 and 8 (not F4 and F8, but 4 and They play just one line at a time. 4 plays only the track you're in, and 8 all tracks.
That's all there is for this specific case.
With multisequence, we may add ways to add loops in exact lines, but don't expect a granularity smaller than one beat.
<[JAZ]> Pa pi pa pa pa pi pa.... ;ĚD