How Do I Create A List Block That Has Category/Sub Category values on the Left In A Dropdown

So I’m trying out a List block where you have List Items on the right (each being displayed as a tile) and Categories on the left (content) which is displayed as either individual Tag fields or Dropdown Tag fields.

In my Items table which populates the List Items on the right, I have a Sub Category field that can be set to a Sub Category ID value for a Sub Category in a Sub Category table. I also do a lookup based on the Sub Category ID value to a Category ID value in the Sub Category table and display the Category ID in the items table.

So for instance, Item 1 in the Items table has a Sub Category ID = to 7 which is a Sub Category for Category 3. In the Sub Category table, ID 7 could equal to Router. And in the Category table, Category 3 could equal to Network.

So to the left of the item tiles in the list, I want to be able to display the Category and Sub Category names in an extended dropdown list for the items displayed in the List on the right, and when the user clicks on either the Category or the Category/Sub Category combination, I want to display all items in the list that have that particular combination of Category and Sub Category.

So you might see on the left


And if you click on Network, you would see all tiles that have the Network Category. And if you click on Modem, you would see all tiles that have Modem Sub Category.

How can I set up the block to do this? Note: I want the values on the left to be automatically populated from the Items table that’s populating the List.