I am totally guessing here, but, it could be calcium build up on your leaves. I notice it more on the stems at the soil line. (absolutely no guarntee this is what you have!)
I have found the "Scrubbing Bubbles" spray that is used to clean bathrooms works really well in ridding the calcium build up on plants. It also shines the plant really well. I spray it on and let it sit a few minutes and rinse it off.
It also helps to use either rain water or allow your tap water to sit a couple days before watering.

Hi Havfaith & Welcome,

I don't think this is a problem, rather can be characteristic of some Hoyas which have 'flecks' or 'splashes' of whitish or silver on them.

When I first started collecting Hoyas more than 5 yrs. ago, a knowledgeable grower (w/ whom I communicated elsewhere), suggested this is actually sugary or nectar-like & said I could likely even scrape some off into my coffee as sweetner. Your description of it being sort of waxy & that it can be scrapped off, suggests to me that's what it is. If you haven't used any insecticides on it, maybe scrape enough off to taste a tiny bit?

Importantly, since you said it's actively growing w/ lots of new growth, I suggest there's no problem & nothing to worry about, enjoy!