Modifying sketches also modify bodies

[karel.works]

Here is official S3D announcement containing videos. That is probably best way

5.620 - Merge History steps

Greatly improve your workflow with these new updates to Design History and Visualization. Design History updates: New: Now you can merge history steps with just a single click to remove dependencies between bodies and sketches. [5.620-merge] Improved: The Project tool now has a new option to project sketches without retaining a connection to their origin, allowing you to make further edits on projected sketches. [5.620-project] Improved: The Project tool can now project items into an existi…

And here is another example:

How to delete Skethes?

Hi Red, If you want to delete them, merge history. [IMG_0072]