We design and maintain a web app for projects monitoring and data visualization. The product is used in an intranet with 500+ users. The main feature of the product is using a dashboard with metrics of projects of the organization. Depending on roles, users can apply filters for the viewed information, search, and have a personal portfolio of projects they are involved or following.
We're interested in defining some UX metrics to inform design team with optimization and improvement of the product based on user data. As I see it the product doesn't have clear conversion goals like for example an eCommerce site, and has very few specifics tasks to measure its completion time. The app is more to explore different aspects of the portfolio and visualize data. Some metrics are already implemented in the app like: most used filters, number of users accessing the app or distribution of users per role.
What would be the best approach or methodology to define UX KPI's in this case?