Is there an option to wipe the trees from the map on the screen (show/hide)?
If not, I would appreciate it. At present I have only found a way to fade them out slightly and to create a tree-less map.
When you "fade them out slightly", they can either be hidden or transparent. Hidden means for trees that each tree is displayed as if it was in an early growth stadium. They can not be removed completely.
If you activate the "smart hide", only objects near the cursor disappear, and in combination with transparency, trees disappear completely, so that's ideal for construction in dense woods.
You can more all tree*.pak into another director, load the map and save it again, move the tree*.pak back, and this map is stays forever treeless.
(https://simutrans-germany.com/wiki/wiki/display724)
The setting of transparency also applies to buildings.