You can export a raster image without any edges if you turn them off in the Styles Edge Settings panel.
If you just want to get rid of the rectangles on your trees, edit them and hide those edges. You might also hide the edges on the pavement between the white stripes or erase them.
Thanks! It worked!
BTW, your profile is confusing. It says you are using SketchUp 2020 which is the desktop version but it says you are using the free version which it isn’t. Please update it so it’s more clear.