The UI for population transfer, as well as path display for it are done. There's some validation stuff that I need to add (checking to ensure that the system is explored and colonized), as well as end-turn processing that generates the actual transports and subtracts population, but most of the hard work is done. I'll let the screenshots speak for themselves. Note in the screenshot, I added a selection border around selected system, tooltip when hovering above button, two buttons under the planet ui's sliders (relocate and transfer), and green path for current transfer plus amount of people transferring in bottom left of UI. It's ironic that the system's random name is "Lies", this is all truth, I insist!
As always, I welcome your feedback!