Bookability box
In order for an item to appear in your online booking flow it needs to be connected to the correct booking step.
You can define the booking steps and which categories of items appear in them in the
In your item you can then define which categories it has and therefore in which booking step it appears.
You can do that in the bookability box:

Here you first find a switch between “Public” and “Internal”.
Internal basically means, that an item will not appear in your booking flow at all.
You would use this for items, which you want to apply manually to a booking (like late return fees). A customer will never be able to select it himself.
With Public on the other hand, you see the individual booking steps and can click on them to open the step and see which categories appear in the step. You can then select a tag / category, like “main object” in this example, to assign this category to the current item and therefore connect it to the step.
Important note:
If you have an item, which should automatically attach itself to other items and is not optional (like a deposit or cleaning fee), then you don’t have to connect it to the step.
You can technically do it, to have the item also appear in let’s say your “extras” step, but it is not necessary for the item to be added to the cart.