I didn’t build a solution like this myself, but I would try the following:
I would use non-persistent entities to drive the values of the dropdown widget. Use a marketplace widget like this one https://marketplace.mendix.com/link/component/118916 or another one that you like.
After you set the first drop-down, the On-Change event can trigger the query filling the non-persistent entity for the second drop-down, etcetera.
Is this the help you are looking for or do you need me to guide you more?
Go Make It
Who can help me answer this question, thank you！！！
What you are looking for is Dependant Reference Selector or Dependent DropDown UI/UX. I dont think there is a out of the box marketplace widget for this. So you may have to go custom.
1 idea is: The first RefSelector is the way you have already done, (via Association from the Context object which encloses the RefSelector Entity) the 2nd and the 3rd Can be created with Datasource as a Microflow.
In each of these 2 Microflows you get the Context Object as the Input Parameter, from which you can get the First RefSelector section using the Association and then as the output of these DS MF’s you return only those values which has the selected Division as relationship.