Fear is giving me the opportunity to improve my techniques and tools
Is that wax or hot snot? If its hot snot and it is stuck to the board as well, good luck with that then.
To me it looks like this Pattex glue:
My guess is hot snot or the rubber cement. Over here, rubber cement is known as Shoe Goo, rather than Pattex. However, patte is french for paw, so is that some wordplay with shoe going on?
If you can press it in slightly and have it rebound, then it is most likely rubber cement. If it does not really press in at all, then more likely the hot snot.
My experience with wax is in the realm of nordic skiing, so that may colour my perspective. To get a nice fillet shape like that, the wax would have to be melted and poured in. Melted wax has a much lower viscosity than hot snot, so there would have to be some sort of vessel/barrier to contain it in place during the pour; not likely worth the effort to do so for something like this. Also, a harder wax that melts at higher temperature is not a good candidate. The melting temperature of the wax is probably not going to be kind (thermally) to the electronic components. A hard wax is more likely to crack in a shock load, so it really does not have the desired mechanical properties. A softer wax that melts at lower temperatures would be more likely to hold the capacitors in place under shock and vibration. However, that softer wax might have a melting point to become liquid under operating temperatures of the electronics; definitely not what you would want. I almost forgot, the test for wax is to scrape the surface. You will get a nice shaving of wax with a softer wax. With a harder wax, the shavings may be smaller and brittle, almost like a powder.
And back I go to cleaning out leaky battery goo from remote controls and kids toys ... I will be averaging more than one a day this week