Element properties can be altered from the Inspector. You also have the option to choose from a list of predefined Styles, using the relevant style selector dropdown.
When you make a change to a property value that has a particular Style as a basis, you get the option to update that Style definition with the new property value.
New custom Styles can also be created. When you have changed property values according to your preferences and then click + New Style, those property values are duplicated to that new Style, then prompted to give it a name. These custom Styles are saved in the Document.