Command Delete Mutation

This setting is the percent probability that an individual, when mutated, will have one of its shapes selected at random and mutated by the deletion of a command in our language of operations from its command list.

This setting is normalized to sum to 85% with

Command Insertion Mutation
Parameter Shape Mutation
Command Change Mutation
Crossover

when you leave this dialog page, so it may not retain the same numeric value when you return, but its relative value will be equivalent. That means that to set this value as high as you can, you must set the others listed above to low values.