Understanding the market landscape and how it breaks down is a good first step. For example, within the broader category of "customer engagement" there are sub categories like marketing and advertising tech, support/enagement channels, call analytics and contact centers and CRM. And then there are even more categories or sub jobs under each (read about the jobs to be done framework if you havent). To help create this 'market map' you can look to industry analysts or the Forrester / Gartner Magic Quadrants but I encourage you to not take these as boilerplate as it's really individual to your company and the way you uniquely view the world.
Once you have the market map, I would identify where you play today and where there are potentially underserved markets. Are there few competitors, sub-jobs not well served, markets that would add value to your current offering, it could even be certain markets in certain geos.
I would use this market map to connect with other teams likely already thinking about these questions like bizops and Product. The market map alone can be a good conversation starter. Ask questions like which of these areas do you think is underserved, where do you think our company is well positioned to play, how might we differentiate in these areas. I would then work with your bizops teams to size the TAM of your top list of 4-5 new markets and make some assumptions about how much share/revenue you could make in the next 2-5 years.