To my understanding, you want to create dynamic dropdown whose list items can depend on the value of other variable(or selection).
From R2021a, you can create dynamic controls in live scripts by linking variables to drop-down items. To populate the items in the drop-down list using values stored in a variable, in the Items > Variable field, select a workspace variable. The variable must be a string array to appear in the list.
So a possible workaround could be:
First Section contains:
p = ["America", "Europe", "Asia"];
p = ["America", "Europe"];
After running this section you will get the variable 'p' in your workspace.
Now, the next section should contain:
Now when you choose the' Customer' value in the dropdown, it will affect the variable 'p' and hence items in the dropdown list of 'Engine' will also change accordingly.