For starters, I would probably change your INDEX to list everything from Top to Bottom instead of right to left. Second, I don’t think there is a way to have one list of INDEX item pointing to several different sheets. I tried setting up a combined column array of relations, just the see if I can use one relation key to link to multiple sheets. It didn’t work and I could only add a list by each individual relation key. I think it mostly will not work because so much in Glide is tied to each individual sheet, and to get multiple sheets to act as one would probably take an entire rewrite of the system.
My first suggestion would be to combine the sheets into one, like has suggested above. It’s the quickest and easiest solution. The next solution would be to use your index sheet as a tab in the app, but ignoring any of the data in that sheet and remove any components that are showing up. The index sheet will be used as a dummy sheet (placeholder for components). Remove all components and then add either a button or a List Relation that will point to each sheet. No need to try to link everything up between the index and other sheets. You will basically build the index in the app with the buttons or list relations. It will look like one list, but actually be separate lists for sheet. Unfortunately you will have to individually setup the layout for each sheet.