You can create a new cell style by copying an existing manual format.
Open the Styles and Formatting window and choose the type of style you want to create.
In the document, select the formatted cell that you want to save as a style.
In the Styles and Formatting window, click on the New Style from Selection icon
.
In the Create Style dialog, type a name for the new style. The list shows the names of existing custom styles of the selected type. Click OK to save the new style.