Good Afternoon,
To accomplish this you have a lot of options I would say the main two are:
1. Power Automate Flow
or
2. Power Apps Collection
Since we are in the Power Automate section let's start there with a quick run through
Power Automate flow: (Note this is AI regenerated to not make you read my writing for all of this)
1. Open Power Automate and create a new Automated Cloud Flow. Set the trigger to run whenever an item is created in any of the 11 individual lists (use the "When an Item is Created" SharePoint trigger).
2. Add a Create Item action to the flow and select the combined list as the target. Map the fields from the original list to the fields in the combined list.
3. In each of the 11 original SharePoint lists, add a new column configured as a Lookup Column to reference the ID field from the combined list.
4. Update the flow by adding an Update Item action after the Create Item step. Configure it to update the original list by assigning the lookup column with the ID of the newly created item in the combined list.
5. Test the flow by adding a new item to one of the original 11 lists. Verify that: The item is created in the combined list. The lookup column in the original list is updated with the ID from the combined list.
If you need the collection feel free to ask but, I think this will solve your problem in the case above you will need a seperate flow for each of the lists you want to copy from.
If you want the entry to not exist in both places (remove it from the list it originally came from) use the delete item action and delete where the ID occurs from the trigger.
I hope this solves your question if it does please select this suggestion as the answer and have a wonderful day.