I have to transport a 4 tiered fondant cake for an event. Once I insert the long dowel to stabilize the tiers, how would you cover-up the hole the dowel makes in top tier fondant? Looking for ideals please

Depends on the cake design as for decoration but why not do the bottom tiers separate from the top? Just make your hole in the bottom of the top tiers board in advance. Measure your bottom tiers for height and add on whatever you want for the top tier. Insert the dowel in the bottom tiers as you usually do and lower the top tier on and presto no hole in the top at all.

Elizabethscakecreations, I never even thought of this. Thank you so much

no problem 

I usually would make the dowel 3 or 4" taller than the cake and once on locations, pull it out, then hide the hole w/a flower or leaf or the top ornament.