Sort of 'main samples-start'?
It's a complex thing because of the loop lenghts and starting time, so I guess there's no solution,
But is it possible to have a function that makes the whole samplemap starts at a different point?
Well, you can simply select all samples and enter a new sample start value (or right click on the field to open a big slider). Loop points should not be affected by this.
If you want to change them dynamically, increase the sample start modulation range of all samples and add a constant modulator (take a look at the tutorial how to use the sample start modulation).