You can not delete those points because you use them later on:
A2 is used to create A3 and both are used for the “detail” “ENCOLURE (dos et devant)”. You would have to delete those first.
If you want to keep that detail but don’t want to see the points, you can blend them out with the group tool (that eye with plus in Operations on the left):
- select the group tool
- select the points (press ctrl)
- press enter after you selected all points and give the group a name
- go to the box “group” on the right (if it is not there, select it under menu Pattern Piece - Group)
- click the little eye on the left side of your group