What does "bolt-on" mean in this Arrow Electronics' job posting?
According to the following sources and the description you gave, I think it means "(optional) extra", or "additional". 


bolt-on (Cambridge dictionary)
bolt-on (Wordreference)


I'm not an English native speaker either, but I'm with Olin Lathrop in that they are using a confusing language/jargon just because they think the ads will seem cooler. 

IMO, wankwords category!