Edited the title and description: I believe the user is interested in additional milestone metrics. The existing milestone system would not need to change, but would require new metrics to meet their request.

Though each one will likely need to be considered independently.

• Investment Growth Rate
• Annual Contributions (although similar to Pre-tax Savings Rate, After-tax Savings)

Inflation Rate (not sure how this would work as a dynamic milestone criterion though since most plans use a fixed inflation rate)

For forward-looking planning purposes, I think safe withdrawal rate is really just a different way to say networth as a multiple of expenses, which you can already do.

— original text: I would love to have more “dynamic” options available in Milestones. A simple example would be calculating the crossover point where annual investment growth is projected to exceed contributions (or possibly 1.5x or 2x contributions). For the most extreme example that I have considered, it would be helpful to be able to calculate CoastFIRE based on the user’s annual living expenses, net worth, preferred safe withdrawal rate (e.g. 3.75%, 4%, 4.5%), Investment Growth Rate, Inflation Rate, and a CoastFIRE retirement year (which might be different from my safe withdrawal rate retirement year.