The Levels Creator tool in the Creators group of the Project Setup tool-set can help create multiple levels at once with various options.
After the button is clicked, the main dialog will appear as follows.
The Revit Length Unit & Precision group displays the length unit and precision of the current project model so that users clearly know what unit and precision are for elevation and height input.
The Height group indicates whether the level heights will be all the same and what the height is, or each level may have different height.
The Level Style group indicates what level styles are available from the current model and which one to use by default for the coming levels. Each level can have different style, which can be set further in the Levels grid.
The Count, Base & Naming group specifies the total level count, how many are above the ground, the base elevation, and level naming convention including prefix, number series and suffix. The Number Series have a lot of different and good options provided. If necessary, the chosen Number Series can be edited further using the Verify/Edit Number Series button.
The Other Settings group can exercise some more control over the coming levels such as which end to show the bubble, whether 3D or 2D extent to use for each end, level types (Structural or Building Story), and whether to delete existing levels if any.
The Operations have a few buttons for taking actions.
The (Re)Populate All Rows will populate the grid with the data input and options as specified.
The Update Existing Rows will get those affected existing rows updated based on some further input or data change.
The Add New Rows will add some new rows to the grid based on the current data input.
The Verify/Edit Number Series button will pop up the following dialog for editing the chosen Level Number Series. After the OK button is clicked, the edition will be saved for use, current and later.
If the OK button (with a green check mark) is pressed, the level candidate as shown in the grid will be created accordingly into the current elevation or section view. For the sample input as shown in the UI, the resultant levels may look like the following:
If the Cancel button (with a red cross symbol) is pressed, the dialog will be dismissed without doing anything to the Revit model.
If any issues during the creation, they will be reported in an information box.