I had difficulties with the video before (and a poor explanation), it should be worked out now:
I want the cylinder on the right to be filled with liquid (left cylinder would be empty), then, as it reaches the the other cylinder and forms a new merged “container” I want the fluid to flow into the new empty space. I was trying too do this with a boolean modifier, but the fluid would just stay contained in the first cylinder, and never flow to other container once they were joined, despite the fact there was no longer a surface to contain it.
Any ideas for me?