As of now, Capitally is already fantastic for tracking return performance of bought investments sliced in various ways. However, another part of investment success is determined is selling at the right time rather than too soon or too late. It would be a great if Capitally would be able to benchmarks the performance of sold investments vs. portfolio returns and indices / other benchmarks.
The rationale behind such a feature is well described in this article: https://www.goodreid.com/Goodreid%20eArticle%20-%20Investment%20Sell%20Discipline-%20%20Exploring%20the%20Counterfactual%20“What-If”%20Scenarios.pdf
I know of one investment tracking tool that tried to implement such as feature (not entirely successful, I think) like this:
There are probably many ways to implement a feature like this from a simple metric to a separate report page, but I’ll leave that to the expert 
. Tracking the performance of sell decisions would be a feature that could potentially set Capitally apart in the future!