Even after creating a Mark, you can edit its appearance, regardless of whether it was
a Mark created from Selection or a Standard Mark
Select the Mark you want to edit
In the Mark Inspector you can see a preview of the
objects used in the Mark ("Mark Content"). In the Inspector, you can also change
its coloring strategy (see Colors and Separations in a Mark).
Click the Edit Content button, or double-click the Mark
while holding the Alt key, to open the Mark Content in a special Editing mode,
e.g. to add or remove objects, change the shape, or change the colors.
Click the Back to Document button to close the Editing
mode, and return to your document window.
The Marks on the document are automatically updated.