It doesn't matter if you are in Calendar mode is activated or is deactivated, you can change the name of meals, add or remove them very easily.
Go to the “Design” section of the plan.
Then click "Edit" under the name of the plan.
To:
add meal, click on the “Add meal +” button.
or the trash can icon to change the amount of meals for the day;
You can move a meal with a simple drag and drop.
To rename a meal, simply click on the name of the meal.
You also have the option to directly add a snack in the plan by clicking "+ Add a snack" under a meal.
Further information
To learn more about “calendar modes”, click here.