Hey there! I’m not from the Prusa Support team but may be able to help.
First of all, do you have another printer that works (assuming that you haven’t finished assembly yet, that is)? If not, I would wait until you’re done with assembly. I found a file on Thingiverse that has a double-sided cover plate for the heatbed cables. However, it’s at a 60-degree angle, which shouldn’t change much (it was designed to be for an enclosure where space is limited). I haven’t used it, but I’m pretty sure the screws are covered completely.
In the about 5 months that I’ve owned my MK3 MMU2, I’ve never had a short. However, it’s not impossible, so if you’re looking for unofficial advice, here it is.
I hope this helps, and good luck!