You can save sets of objects as a "blueprint" and place these later.
This is handy for reusing common parts between parks, or making a noteworthy (be it compact or high-excitement) coaster design and then making variations of it in different parks.
You can also download blueprints from Steam Workshop or mod.io. Placing down other people's designs can be less interesting, however: looking at what other people are doing can still be valuable to study ride elements or decoration tricks.