All I've been able to find is:
1.
Avoid adding to much in the first place, to avoid the problem. (Everyone says this.)
Several sites said or implied that adding too much manure can add excessive potassium. Maybe some people keep adding more manure to get plenty of N, even if the N is consumed every year. They KEEP adding more manure every year and the K accumulates more than the N.
2.
Wait for it to leach out. (Many sites say this, or just say "wait for it to get better".) Do you have plenty of rainfall? Drainage that carries water AWAY from your beds before it evaporates or is pulled into plants.
3.
Another site says not to trust soil tests (???) and also to be sure you took your samples from soil deeper than the top 3".
The part I agree with is that if the lab says your K is too high, but your plants are growing well, don't lie awake at night worrying. Just avoid adding more K!
4.
One site referred to the ration of Ca:K and suggested adding some Ca if you aren't already high in it.
5.
One site suggested growing some crops that aggressively suck up nutrients, like alfalfa. But then you would have to move the leaves and stems away from those beds! Feed it to livestock and then don't use their manure? Use it as mulch on beds that tolerate high K? Bale it and sell it?
I don't know, but expect that it does leach out over several years if you have sufficient rainfall and sufficient drainage.
The raised beds do sound like a good solution while waiting for leaching to occur. I hope you don't have to irrigate to get some leaching going!
