Hopefully someone will release a save-game editor soon that allows for easy searching of the unique ID of newly built stadiums. But until then I will try and explain how I managed to work out the stadium ID of my new stadium within my save-game in order to help anyone interested in finding the ID of their own new stadiums.
The Basics
By looking through the dates when newgens (and their unique IDs) were created in various countries within the game, I managed to find a small range of IDs in which my new stadium ID would likely be contained. By assigning different background pictures to each ID within this range I managed to pinpoint the exact unique ID of my stadium.
My Example
As I play in England, news of my new stadium was first announced on the 17th June 2018 (to be completed in June 2019). The two closest newgen creation dates in my save-game were the 7th June 2018 (Albania, Bosnia, Cyprus, Estonia, Macedonia, Georgia, Latvia, Lithuania, Moldova and Montenegro) and the 20th June 2018 (Croatia, England, France, Germany, Greece, Hungary, N.Ireland, Portugal, Scotland, Switzerland, Turkey, and Wales).
From this information I speculated that my new stadium ID would be located between the unique IDs of the last player created on the 7th June and the first player created on the 20th June 2018. By noting the unique ID of the players promoted into each club within the first set of nations mentioned above, I found the last player to be created on the 7th June 2018 i.e. the one with the highest unique ID, was 2000077627. As my game has normal database size, only 27 newgens were created by these 10 countries and therefore this part was not too difficult.
Now looking at the 20th June update, I needed to find the first newgen created on this day in order to find their unique ID and give me the top part of the range I was looking for. Croatia’s newgens had the lowest unique IDs and therefore noting each Croatian newgen created on the 20th June 2018 I managed to find the first player created on this date i.e. the one with the lowest unique ID, was 2000077665.
I now knew my stadium ID was located between 2000077627 and 2000077665, a possibility of 37 different IDs. By using an existing stadium picture config file (e.g. one found in Beefsters stadium pack) I added a line assigning a certain picture to each of the possible 37 unique IDs. By checking my game, I could see which picture was now appearing as my stadium background and could finally note the corresponding unique ID I had assigned within the config file. It turned out my new stadium ID was 2000077639
For anyone attempting to try this feel free to ask any questions as the process is quite difficult to explain due to each person's save game being unique in terms of database size, stadium creation date etc. Anyway i hope this explaination helps those who require it. :thup: