Not every shop needs the Markup % to be visible on every Line Item Group and/or sometimes the custom product has the markup built into the price so overriding the Markup % is unnecessary.
Super Admin users can now set the Markup % column to be hidden instead of visible by default on a new Line Item Group in My Account > Customize Your Line Items.
Unchecking/checking default visibility does NOT effect existing Line Item Groups.
Show/Hide per Line Item Group
Just like the other size option columns the Markup % can be checked to show/hide per Line Item Group.
Dragging a Line Item with a custom Markup % value will render the column visible on a Line Item Group that has a default hidden Markup % column and an Imprint with a Pricing Matrix applied.