There are 3 different ways to add multiple blocks to checkout, each with their own strengths and weaknesses.

Using multiple app blocks

Add 1 new app block for each block.

This is a simple way to add multiple blocks but each “slot” within the checkout editor can currently only hold 3 app blocks, so this may not be the most space efficient method.

We also recommend setting the Fixed block ID setting within each app block to ensure consistency.

Using 1 app block with multiple Fixed block IDs

The Fixed block ID setting allows for only 1 active block to be loaded at a given time, but if your blocks are all mutually exclusive in their display rules then this method will work great as the app block will load the appropriate block given the situation:

This can be a great way to overcome the 3 app block per slot restriction in the previous method.

For example, if you have several blocks that are each set to show for different markets, or if you have 1 block set to show for under $100, another block to show between $100 and $200, and another block set to show for cart totals over $300, then this configuration will show the appropriate block corresponding to the cart total, all while using only 1 app block in the Checkout Editor.

Using 1 app block with the “Multiple block IDs” setting

Similar to the Fixed block IDs setting, but this setting will show all specified blocks simultaneously.

This is a relatively newer feature and is currently not compatible with upsell/cross sell blocks, or use with the Fixed block ID setting.