I can only get retrivability now. Im trying to tag difficult cards tomorrow 
They are mostly the same, but i always miss a few cards. Specially cards that decay fast
And a second question, since it is dependable on the time, is the % calculated every time i open the browser or is it calculated once per day?
Thanks
Is it possible to search for cards due tomorrow with retrivability (tomorrow)<.5
Sure: prop:due=1 prop:r<0.5.
That returns card with r<0.5 today that are due tomorrow
I want card that will have r<0.5 tomorrow
I’m not aware of any tools that will allow you to search for a characteristic of the card that isn’t currently stored in the database. If it won’t be r<0.5 until tomorrow, you can’t search for that with R.
However, if you have cards where R is decaying that fast, surely they have very low Stability as well, right? Since S isn’t recalculated continuously like R, you should be able to search by that. I don’t have any low S cards right now, so I can’t tell you for sure how fractional days are stored, but prop:due=1 prop:s<=1 should be a good place to start – maybe add another term for R being less than something, but you’ll know more after you start running searches in your own collection and see what values would be useful.
Yeah i think that might work. Thanks!
On the other question, do you know when is retrivability calculated?
And a request/suggestion for the ankitects that probably deserves its own thread. I also noticed that it returns different results in card and in note mode simply because note must be an average of the cards. Being able to add a marker to the search to let know if you want notes or cards return would be useful for saved searches in the browser (and for filtered decks too :))
When the card is studied, when the memory state is recalculated (optimization, rescheduling), or otherwise it decrements daily.
Some card-level properties show up as an average in Notes mode, some show one of the extremes, or a total – Browsing - Anki Manual . But if you want to avoid confusion on this, just don’t have the column for R (or other card-specific information) showing in Notes mode.
I don’t think that searches return different results based on Notes mode or Cards mode – choosing the mode just dictates which information is shown (and which set of columns, see the link above). If you search for note-level properties (field contents, tags, note types, etc.), you’ll get a note or all cards that are made from that note. If you search for card-level properties (state, scheduling, flags, memory state, etc.), you’ll get a specific card or the note that made the card.
A change like that wouldn’t make sense in Filtered decks, which (like all decks) only hold cards.