How to demonstrate leadership when you are not the boss and the company is not a traditional startup?

So, I have been working at a company that is small but old (around 25 employees). Basically, the company was founded many years ago and got stuck in a niche market. But there is a new product that we started selling and it has a huge potential (it has patents and clients are impressed). There are two groups in the company, one that my boss is part of and consists of some old folks from this first generation and they are pretty much "settled" - they have been working for the company for many years, never got good raises or mentorship and at the same time they were never asked for goals either, so they just work for a paycheck. Some people even started businesses on the side. The second group is the new folks who are younger, motivated and we are pushing this new product really well. I'm working very close to the product manager and he really likes my work. I'm not junior but I'm not also a manager, but I really wanted to demonstrate leadership as I already know more than my boss (he is sort of a marketing manager / general manager). He has a good relationship with me and I don't to screw that up, but at the same time he doesn't care much about my development and he gives me work to do that should be done by interns (like filling documents or making updates on the website). The product manager already wants me on his team to work full-time as a product designer / front-end developer. I also developed respect from other developers, I have this unique skill in the company which is the understanding of front-end, design, and human behavior. Everybody likes me, but I don't want to be seen as the "nice guy", sometimes I actually think I'm too nice. The owner is true decision-maker and he has a good relationship with my boss who has been working at the company for 10 years. So, I'm basically thinking on ways that I can demonstrate leadership to expose me to the owner, such as doing hackathons, or special projects like something for business intelligence, but I really don't know what would have the highest impact. On the other side, I can do things such as changing design process, usability studies, and a lot of things that will improve my knowledge, but might not get exposure and that might never lead me to management. I understand that from a business perspective what makes employees valuable is what kind of value that they bring to the company, so I'm thinking how I can do something that it will truly expose me as a leader? Note: we are not data driven, so many things are decided on feeling. Unfortunately, I don't have natural leadership skills mostly because of my disability - I have ADHD and I struggle with oral communication). I'm also not an English native speaker, but I improved a lot recently because I was coached by a previous manager at another company that I worked for. I also started taking medication which improved my speech glitches a lot (I used to forget words all the time and get nervous), now it's much better, but I still have some baggage - years of low self-confidence behaviors that shaped my personality.