The Metadata can be used to get cascade variables/Values, which allows to fetch corresponding subcategory by pulling from its parent category.
Alternatively you may use data-list and lookup to implement.
Step 1 - Create Metadata with cascade
Let's create a Metadata in Settings. please refer to Metadata management.
In this example, we have a metadata named "Expense Type", and we will see the cascade from ① -->②-->③
Step 2 - Set Metadata in Form Designer
Go to Form Designer.
Let's drag and drop three Metadata controls according to our example, You may add more cascades as required. All variables should be bound to the same Metadata.
The first is the Parent-category 1, which is no associated parent (unless you want to set it from its subcategory).Always the "Hierarchy" is off as default.
The second is the Subcategory 2, which should be associated with parent variable of "Parent-category 1".
If more, then the third is the Subcategory 3, which is associated with parent variable of "Subcategory 2".
Then let's set the "Dynamic Display Rules
" in subcategory 2&3, which makes a cascade view.
Step 3 - Manage the layout and Publish
Preview and check the results before it publishes.
Furthermore
In some scenarios, you can also use it in list control/variable and get the same effect.