I am new to this so excuse me if I am asking an already answered question. I like to work with about 20 to 30 slides at a time, using custom synchronisation. My problem is that when I add a second or subsequent batch of slides, I have to go through manually and add transition points one at a time for each new slide. Is there any way I can just add the extra 20 to 30 with a general synchronisation, without destroying what I have already done?