The BBC ECU Guidelines state that:
You should make your complaint within 30 working days of the date on which the content was broadcast or published. Exceptionally, the BBC may still consider your complaint, but only if it decides there was a good reason for the delay.
However
Complaints about BBC iPlayer and BBC Sounds should be made within 30 working days of the content ceasing to be available.
This “ceasing to be available” means that we effectively have until June 13, 2024 to submit new complaints. Feel free to use ADHD UK excellent step-by-step guide: https://adhduk.co.uk/complain-to-the-bbc/
If you decide to complain - feel free to follow ADHDUKs’ excellent guide, but keep in mind the 30 day rule and needing to address it:
Complain to the BBC - Quick guide to telling the BBC your opinion on Panorama