How would you implement virtual scrolling from scratch for a list with 100,000 rows, including support for variable row heights and dynamic content?

Imagine you have a huge coloring book with 100,000 pages, but you can only see one page at a time. Virtual scrolling is like having magic glasses that only draw the page you're looking at, and as you turn the page, it quickly draws the next one. This way, you don't have to carry the whole heavy book around.