Let's say 50% of All visitors are landing in an A/B Activity_1, which is live. Now, I want to utilize the 50% of All visitors who have not landed in first activity, for second A/B activity. Is there a way to configure audience in such scenario?
Based on your scenario it is a possibility that both the activities would collide with each other which would affect content delivery and reporting. The best approach that I would recommend in this case where you want the visitors to enter both the activities almost equally would be to create a profile script for a random number generator and based on the output if the result is even or odd assign the visitors to activity A and B respectively.