Yes, I can relate. I had crippling panic attacks on and off for about 7+ years. I didn't want to take meds for it although I was close to doing so at the start. I ended up learning about ways I could improve my daily lifestyle and went the holistic route. I too tried some of the things you had mentioned Meditation, breathing and visualization techniques, walking in nature, qi gong, exercise, supplementation, positive thinking, dietary changes etc. But at the time I was struggling quite hard financially and that was where the source of the stress was coming from. So until that started to ease up and get better I was a bit of a mess.
Over time it got better slowly but surely. They became less and less frequent now I don't have them anymore. I used to get the rarer sort of panic attacks too. The ones that would last for hours at a time. So to say it was frightening and very taxing is an understatement that some of you on here may understand all too well.
Learning about the vagus nerve and vagal toning massage was a total game changer for me though. The exercises can be found on YouTube and are simple fast and really effective in bringing the nervous system back into balance. Out of all the things I tried to do in the beginning none of that ended up being as effective as doing vagal toning exercises. I highly recommend adding that to your anti anxiety tool belt!