Hi!!
I think that you would have to create different heatmap questions inside the block that you are going to loop and merge, and apply to each question display logic based on the loop and merge that you want to show it.
For example, If you are looping based on some brands that the person chose, you want to show and specific heatmap for Brand1 and other for Brand2, you create 2 heatmap questions and apply to each of those questions Display Logic, based on loop and merge depending on the loop corresponding to each brand
For the block:
Hope this works! :)