I have a marginata plant (indoor) that has grown more than 3 feet tall. I am planning to trim the branches and transplant into a bigger pot. Couple of questions-
1. What should I fill the pot with in addition to potting soil?
It's a huge resin pot. Hence looking for pointers. Thanks.

Dracaena marginatas do not do well in large pots as they are prone to root rot. In addition, their root systems are easily traumatized if repotting is done unnecessarily or incorrectly.

Pruning is fine, but why do you think it needs to be transplanted? Can you post a photo of the Marginata?

Thank you for your response. Here's a picture for reference.

Very nice plant! It has been recently grown in a greenhouse under ideal conditions. That means that it will lose some lower leaves as it adjusts to the reduced light in your home. It also means that the roots will gradually shrink back in size. That is why I don't recommend, moving it to a larger pot even as it looks like it might need one.

You might consider lifting it out of its pot a bit and repositioning it slightly in the same pot so it is more upright. But that is a more about personal taste. Keep in mind, that new growth will come in only at the ends of each stem and will grow toward the light. Thus, you may want to position the plant so that the weaker side faces the window.

Pruning is another way to manage the overall appearance, shape, and size of your Matrginata. Any stem can be pruned off as much as you want. New growth will emerge just below the pruning cut on any stem, so pruning is a way for you to control where new growth occurs.

Marginata stem cuttings do not propagate easily when put in water or damp soil. If propagating is important to you, then air-layering is the better way to go.

Thanks so much! That's a wealth of info! No propagation for now. Only maintenance!

Your plant may be a Yucca: Spineless Yucca (Yucca gigantea)

The leaves are too thin to be a Yucca. It is a Dracaena marginata.