Since Bear doesn’t support ssaved custom searches]], the only workaround to achieve that is to save a note with a lost of links to these custom searches.
The ones I use the most are
Created today
bear://x-callback-url/search?term=@ctoday%20-%23Reference
Modified today
bear://x-callback-url/search?term=@today%20-%23Reference
Modified yesterday
bear://x-callback-url/search?term=@yesterday%20-%23Reference
Created in the last 7 days
bear://x-callback-url/search?term=@created7days%20-%23Reference
Modified in the last 7 days
bear://x-callback-url/search?term=@last7days%20-%23Reference
Travel journals
bear://x-callback-url/search?term=%23Journal%20%23Travel/Trips