At the moment there is only a single review setting that applies to ALL collections.
The problem is that as you move through a language, your review needs will change. When you start out, 100 Most Common (for example) will need to be hit again, and again, and again. As the questions start to stick you will (hopefully) want to review them less frequently. And eventually, hardly ever.
The 500 Most Common will then need to be reviewed frequently, then less frequently, etc, etc.
Then it’s on to the 1000 Most Common, and so on.
Eventually there may be some collections that you don’t want to review at all and you can set anything mastered to Never.
A “One size fits all” solution doesn’t work well. If you’re doing, say, your 500 most common collection and set your review time to 300 days, then forget to reset that before you go on to your 2000 Most Common one, the only solution is to curse a little and reset the 2000 collection and start again… or not see those questions again for another 300 days even though you haven’t REALLY mastered them.
Or the reverse, if you had set one of your tougher collection to 7 days, and forgot to reset that before going back to your 100 Most Common (which you can recite by heart)… that 100 Most Common will be back in a week.
The “One Shot” review cycle seems to be optimised for Fluency Fast Track which I regret starting in Italian, and am not going anywhere near in German.
If we retained the default cycle but were able to change the cycles of individual collections, we would be able to adjust the review cycle to match our progress in each collection.