Filter the select boxes data based on the cascading drop-down fields selection

Hi @Nas H.

Here are a few option I would suggest looking at:

Dynamically Select-box components

The easiest way to display a different list of select box options might be to make multiple copies of the select-box component, each with a different set of options. You can then dynamically hide/show the different copies of the select box based not he drop down menu selection above it.

Use a multi-select Drop-down

Im assuming you are using the select-box component to allow the user to select multiple items from a pre-defined list of options. This can also be achieved by using a drop-down menu/SharePoint drop-down configured to allow multiple. You can do this by navigating the data tab for the component and ticking the "Multiple values". The benefit of this is you can use the same method you used in the preceding components to cascade the list of options. Heres what a multi-select drop down looks like to the end user.