In most places the concepts you develop while on their dime still belong to them. So even if it doesn’t make it to market or gets shelved, it’s still part of their idea database that belongs to them, and there may be things there that they decide to revisit a year later so if you show it, you just screwed up any potential patent apps, etc… If you do it on their time, it’s theirs, regardless of if they use it or not. Best bet is to just use your improved skillset to do your own made up projects on the side for your portfolio. And that can be better since you won’t be limited by things such as a boss changing things on you, or a tight deadline like you would for what you did professionally. Just come up with your own stuff unless it’s something completely done and on the market.