Here's a graphic of my request:
I hope it explains it clearly. No matter where you cut it or how many times you cut, the pattern always starts from the beginning.
For the record, I thought the slip tool could do this but it doesn't work for patterns.
Right now there is two unnecessary way to do this:
1. Convert pattern to instrument part, cut it where you want it, and convert it back to a pattern.
2. Create a new variation and manually program the drums just as same as where you wanted the cut from.
Maybe a feature like "create a variation from selected" might work, or you can make a tickbox for the pattern to start over when it's split/cut. Or better, both.