Tiled Selection Overhead Layout

Hello all! I am looking to create a top down game low attention game where the player builds various businesses or whatever. I want to use this layout as part of a game serious. So the player, when in edit mode, would be able to click on a tile and select what to place there. So suppose we have a 3x3 grid. As a simple example, the player could select the top right tile and place a grill. Then select the bottom left and place a table. So now you can cook and serve. The tricker part yet is interacting between tiles. You would need to build a chair next to the table, where the AI knows this is a valid sitting spot, and a standing spot next to the grill for cooking, again so the cook can know there is an adjacent cooking location. When it comes down to it I am having trouble determining how to make an interactable tile layout (ideally not visually tiled when not in edit mode), that also serves as a navmesh valid surface. Any ideas?