Board Thread:Plants vs. Zombies 2/@comment-7503158-20150927105902/@comment-24275721-20150929214117

Mr. Boss-inator wrote: Yeah, no 9th slot bothers me too. But they can add a scroll feature, so basically increase amount of "addable" seed slots to infinity. Sadly that is not possible. When you're playing a level, having more than 10 will require you to scroll up and down to put plants on the lawn and in tough levels where timing is necessary, you will be screwed big time.

Also, from a technical standpoint it isn't possible as there has to be an upper limit.