Can a rainbow eucalyptus tree be dwarfed, similar to the bonsai process ?
Certified GKH Gardening Expert
This can be done, although it is a bit tricky. The first few years will be relatively easy, but after you will require some root and top pruning. I would only advise cutting off 1/3 of the roots at the bottom so you do not kill the tree. Dolomitic lime will be your best friend in container, as it keeps the pH stable, as well as providing calcium and magnesium. These are two very common deficiencies in contain.
Here is an article that will help: https://www.gardeningknowhow.com/ornamental/trees/eucalyptus/eucalyptus-houseplants.htm