When creating a map you can have regions that share the same data. To make this easier you can use the region code for the different regions in one entry alone, separating each region code with a comma, like the screenshot shows below:
This is valid for all maps you create. This will allow you to save time and avoid repeated entries. If the entries will share the same data (tooltip, colour, etc) you can use this approach.
Consider the codes should respect the lowercase/uppercase format of the region codes listed on the right column. Depending on the maps, these might be lowercase or uppercase. So check the table of codes on the right side of the screen.
Below is an example of a map of the world where some regions are grouped together.