Just another IC here but I've seen middle managers just bureaucratize an existing process for their benefit. Something like: a) identify a process that is working well/delivering results b) insert a reporting procedure/step for everyone to now follow on the process (e.g. Google Forms) c) manager then builds a weekly report on reporting data collected d) manager circulates their report up/down the org to show their value as part of successful process e) bonus: internally tout the innovative new reporting process as a big win and highlight the 100% adoption rate achieved

So, if all these "colleagues all throughout the org" come to you, you could potentially put in place a request process to document and report on all these interactions and what you delivered. So your metrics are the number of requests you handle and the "successful outcomes" are just fulfilling those requests. In short, document everything. Lot's of unnecessary busywork to gatekeep your access? Yes, but there's your "tangible output".