I had difficulties in deleting curves, lines and points in a pattern piece. Most of them did not show up as deletable.
Some advice to those newbies in a similar struggle: 1) You may have added the curves and lines in Draw mode and details tab, and moved to Details mode to create the pattern layout. If the object is connected to a pattern in details - it will not be deletable. In Details mode: Right click and delete the pattern there. Go back to Draw mode and right klick on objects you want to delete.
2) Back in Draw mode: If the object is not deletable. Make sure it is not connected to a pattern ( "1)" ). Make sure it is not used as a base for another formula or as the base for a line, curve, point etc.
An interesting project you have going on with Valentina. Congratulations to all contributors!