Rereading the question, OP works at a company servicing a SAAS for developers to share code and being paid for it; so far so good. OP works on the backend software for this platform, very well as well.
He wants to sell his Code and Ideas, this is fair. But why has he have to do this in company time? In the question this reads as an imperative? Why can't he do it in his free time like everybody else, using the very same platform he has so much insight in?
Would the code he wants to sell be pertinent to the SAAS platform itself? That might be a bad Idea from the company's point of view for sure.
Or can't he produce non-trivial code one could find on Github or somewhere else in his spare time, because of lack of time or energy or of other reasons like having a life? Well that would mean that he'd work on his own projects on company time, something again any company would find a bad idea for sure as well.
OP's situation is definitely not one of a contractor who writes software or modules from scratch or based on an unique skill-set which is licensed out, and he is NOT producing a product or software in itself, but amends to a (presumably) pre-existing (as in existing at the company before he was hired) software in form of (sic) add-ins presumably ordered by the companies' customers in the first place.
I cannot see a company entering a contractual situation with anyone on these premises unless there would be a BIG benefit for said company.
Don't get me wrong, OP might be a gifted, hardworking, very creative Individual, which could be a BIG benefit for the company to keep and give free reign. But then again as a Company I would argue to advance OP inside its structure, giving a fancy job title, higher payment and so on, as this would benefit the company much more than to allow OP to make money independently from the companies software.
My advise to OP, if (s)he sees him/herself to be a rather free spirit is to break free from corporate shackles and try to stand on their own feet, and create great software, of which one might be the next big thing, get bought by a bigger company and help yourself to those nifty shares!
Otherwise find good use with those good ties to upper management and advance yourself inside the company, working towards the better payday and create some great software, of which one might be the next big thing, go IPO, and help yourself to those nifty shares!
its your choice