I recently transplanted my hibiscus plant from this summer. I've never had one before and it is quite large in the house. Some of the leaves are turning yellow and falling off.
When and How Do You Trim a Hisbiscus Plant?
Certified GKH Gardening Expert
As long as it is in the house, you can cut it back by up to 1/3 before bringing it indoors. Otherwise, you should wait till spring. This article will help: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/tips-for-pruning-hibiscus-plants-when-to-prune-hibiscus.htm
The yellowing and leaf drop signal that the plant is getting ready for dormancy and is normal. This article should also help: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/wintering-hibiscus-indoors-winter-care-for-hibiscus.htm