Hi dodoburd !
I'm developing https://mods.factorio.com/mod/GUI_Unifyer and you're currently the only mod I encountered that destroys and recreates the top left button everytime the gui is clicked. I guess you do that to update the number, but you can simply do that by doing flow.toggle_saved_logistics_layouts.number = logistics.count_layouts(), and the way you delete the button every time does 2 things: it moves the button to the right sometimes, and it prevents me from changing its style.

Are you still active? Would you be willing to act a pull request if I sent you one? (I'm asking before doing efforts if you're not there anymore :) )