Change default DR value for existing users

Anki Suggestions
1

This suggestion is only useful temporarily. For the default desired retention value, we can perhaps use the average retention of the user instead of 90%. This would reduce the chances of users facing really high or low review workloads when we get the switch to FSRS from SM2.

Of course, it wouldn’t be perfect but IMO still better than starting off existing users who switch to FSRS with a DR of 90%.

2

I think this idea has merit.

I would add: when a user begins using FSRS, it is beneficial for him to understand the basics of what “Desired retention” means and why he may want a value different from historical retention.