>>> I think I recall something about COPD which I have, weakening one side of the heart leading to Oedema.
Is that right?
Yup. Explained here:
https://copd.net/symptoms/swelling/
The treatments that your GP
might consider are listed under 'Management' here:
https://copd.net/symptoms/swelling/
However I doubt that there's much that you can do yourself, other than trying to ensure that you get as much exercise for your lower limbs as you can (even if it's really quite minimal) and keeping your legs elevated wherever possible.
I'm struggling with 'tree trunk legs' myself at the moment (cancer-related lymphoedema), which means that I can't walk that far. However, following the advice I've been given, I'm trying to do at least a bit of walking every day and taking some breaks periodically, with my feet up, in between periods sitting at my desk or in an armchair.