If you want repeated objects such as a footpath or road you can create a spline though this may lag your computer if it isn’t powerful enough
A tree/foliage you can add those in foliage editor (Shift+F4) and add a foliage.
If you just want to copy normal objects like make an army of statues or something just alt and drag and when you have about 10 or 50 alt and drag all of those.
