Help with creating a hook up accessory to my custom made accessory

[ApoorvPal]

Hi everyone,

I am new to Blender Tools and recently got my first export (board) into the game successfully. I am trying to add a hookup accessory (cube) to that. I added a model locator in the board accessory and chose the hookup: accessory_addon_data for the cube from the hookup library. Then I made the second accessory (cube) and packed it into a mod. When I try to add these accessories onto my truck, the board accessory turns up fine on its slot. But when i try to add the secondary/hookup accessory by clicking its slot, "No accessories match these filters" turns up on the left panel.

The slot for the board was there on the truck initially. But I created the secondary slot and it's hookup type is a custom new one. Do I need to define something additional here for the cube to show up in the secondary slot?

EDIT: I went through the default def files. Is there a accessory_addon_hookup or something like that in vehicle/ truck
/ addon_lookup which I need to change or add for the hook up accessory to show up?

Thanks,
Apoorv