Here's an idea I've had for a long time but decided to finally make a formal request.
Currently you have to navigate to 3 different submenus to set all 3 thumbnail text options: the text expression; text line count; text justification. Seems like it would be easy to modify the current expression dialog so all three items were shown in a single place. I mocked up the pix below as one possible way to lay it out.
However you do it, the main menu click takes you straight to the all-in-one dialog without any need submenus - having all three in this single location would be so much more convenient. The thumbnail spacing/stack icon submenu would still exist for those options. Huh… but now that I think about it, those other options could also be incorporated into the same all-encompassing dialog too. Oh well - no time to mock that up this morning.
In any event, I hope you like the idea and that we might see this in the future build.