You are not LIMITED to 15 Bosses. You can have more, but only the first 15 will show at once. And that includes World Boss(es) and your Co-op Boss.
your behind dude been suggested alot i even suggested a filter system which hasnt happened as of yet newest boss to oldest oldest boss to newest most attacks to least least attacks to most toughest to weakest weakest to toughest even if some type of filter system were added would help alot more
seen this topic before. yes only 15 not the last 5 you attaked, but the oldest expiring 15 bosses. AS good suggestion. better if you have type category. like all eel, all curse pirate, all mizuchi etc. TIP. save the Boss link on your bookmark. So everytime you can check all boss. i have around 20-25 at a time. i only view the kano bosses when i check my boss and the world boss.
I just do the minimum damage to get rewards and check em off as they are killed and collect the rewards. I'll probably have up to 30 bosses sometimes. Never ran into a problem with only seeing 15 of them because once you collect the reward that boss goes away and up pops the next one who may or may not be dead yet. LeE OTM