Chapter points are created in the "Timeline" of the clip. All of your 30, 10sec animations would have to be in one MPEG or AVI file. Create a "timeline" with Encore, you can choose the option to "import as timeline" and choose your MPEG or AVI. In the timeline view for the clip there is a button to add a chapter point. Thing to remember is Encore will only place a chapter point at an I-frame (the long vertical marks along the bottom of the time line) when dealing with an MPEG...this might make it tricky to place chapter points at the beginning of each animation. Using an AVI and placing you chapter points, and then having Encore transcode the AVI to MPEG will create I-frames for you at those chapter points.
You could also do this with Premiere, using Premiere to place chapter points and encode the video for you with chapter points. Then import the mpeg into Encore as a timeline.