I have been working on and off on the Austrian staff and its development during the Napoleonic Wars. I am currently revamping some of my ideas after looking at Zeinar's history https://www.google.co.uk/books/edition/Geschichte_des_%C3%B6sterreichischen_General/QGuQsTM8LCMC?hl=en&gbpv=1&dq=%C3%B6sterreichischer+generalstab&printsec=frontcover
We have dealt with the myths surrounding Bourcet and the French staff in this long thread https://www.thenapoleonicwars.net/forum/general-discussions/chief-of-staff/dl-681c30bf-94b7-33d9-bc4b-7171dd3612c1?postId=5e238bba0b5ca80055a44327&searchTerm=Bourcet There was also a lot of communication between Austrian and Prussian officers during the wars, but we can date Scharnhorst's reforms in Prussia to 1803. Before that, he had been an officer in the Hanoverian army and as early as 1793, had been advocating a collective intellect to direct armies - Chuck White summarises https://journals.sagepub.com/doi/10.1177/0968344518816720?icid=int.sj-abstract.similar-articles.9 but his assertion that Scharnhorst set up the first modern staff overlooks the fact that in 1793, the Hanoverians were under the Duke of York supporting the Austrians under Coburg!
So, I was interested to see/pinch this from a recent post on TMP - it is an MA thesis on the changes in the British staff and you can download it for free https://www.academia.edu/94398720/From_Total_Ignorance_to_One_of_the_Finest_Bodies_of_Staff_Officers_in_Europe_The_Reform_of_the_Quartermaster_General_s_Department_and_its_impact_on_the_performance_of_the_British_Army_1795_1814?rhid=27660119780&swp=rr-rw-wc-80318476