Is there any knowledge/wisdom/insight that cannot be expressed as a proposition?
One thing I know is the difference between the taste of sangiovese and pinot nero -- a bit of wine-wisdom I've acquired over the years. But I certainly would be very hard put to express that knowledge in propositional form, at least in any informative way that could usefully convey my knowledge to you. Is there any proposition I could use to do that?
Of course, I can say -- taking a sip -- "this one is sangiovese", and -- taking another sip -- "that one is pinot nero". But that won't help you, unless you are sipping away from the same wines, and you are attending to the differences.
You need to experience the wines for yourself, and need to pay attention to them and learn to tell them apart. And developing that skill, that know-how, seems to require something other than picking up propositional knowledge-that about the wines.