Sorry, there's a lot here about the technical implementation details but much less I can understand about the problem being solved. What exactly do you mean by "manage"? What happens differently when you use this command, versus when you use built-in `cd`?
Although you don't have any problems with lag, it is possible to efficiently compute frecency in O(1) complexity
> But with an additional trick, no recomputation is necessary. The trick is to store in the database something with units of date...
Full details: https://wiki.mozilla.org/User:Jesse/NewFrecency#Efficient_co...
I mean, cool stuff. But does it really matter from usability perspective?