How do you select another polygon if you mistakenly with the knifeNode already split one polygon ? I inserted a group node before the knifeNode with bounding box set to cube to select all polygon within the bounding box but the other polygons are not being split with the knifeNode which comes obviously after ?

There is an action button right next to the group parameter where the selected polygons are listed. Click that, adjust selection and hit enter to apply.

Thanks, I appreciate it