The two most well known species of the umbrella tree are the Schefflera arboricola (dwarf umbrella tree), and its close relative Schefflera actinophylla.
Size is the main difference between the two.As the name implies, the dwarf umbrella tree, S. arboricola, is a smaller version of S. acinophylla.
With the larger Schefflera, the leaves are 4 – 5 inches or longer in length. Whereas the dwarf umbrella tree has leaves 4 – 5 inches or shorter in length.
There’s also a difference in height. Indoors, S. acinophylla can grow to heights of 6 – 10 feet. S. arboricola will grow 4 – 8 feet. Either way, both can make for large indoor plants.

Your Umbrella Tree is the non-dwarf type.

Regarding Light:
Schefflera’s like lots of bright, indirect like. They can tolerate a small amount of direct sunlight, but too much and the leaves may burn. Keep this in mind when placing it next to a window.

Though it prefers bright light, your umbrella tree will tolerate moderate to lower light. But it may not grow as fast. Also, too low a light can cause it to become leggy and floppy.

Occasionally turn your umbrella tree so that all sides are exposed to the brightest light. This is especially important if you notice one side of the tree is growing fuller than the other. Or, if you find the plant stretching towards the light, which is what seems to be happening to your plant.

Pruning:
Scheffleras like pruning. Pruning is one of the biggest tasks with umbrella tree care, however, they rebound quickly, so don’t be afraid to prune aggressively.

When pruning, start with removing anything leggy or overgrown, as well as any dead or dying leaves.  To make your plant thicker and keep its height manageable, cut off the top of the stalk, just above the node. This will encourage the plant to grow outwards, as well as upwards.

Repotting:
In general, plan on moving your Schefflera to a larger pot about once every two to three years, sooner if notice the roots breaking through the top or bottom of the soil. Since you mention that your plant has been re-potted twice already, you are already familiar with how to do this.

Additionally, as your Schefflera grows, you may need to provide support for its trunk. I see in your photos that you already are staking the main trunk.

Propagating Your Schefflera:
The simplest way to propagate your Schefflera is to grow a stem cutting in soil or water. With either method, start by using a clean, sharp knife or pruners and cut at least 4 to 6 inches of stem.

Just like with pruning, cut slightly above the leaf node. Since regular pruning is part of good umbrella tree care, a good time to propagate is in spring right after a pruning. Leftover cuttings make great propagating material. Remove the bottom leaves from the cuttings.

It’s important to not let the stem dry out. So, if the cutting is not placed in water or soil immediately, wrap the stem in a damp paper towel. Keep the towel wet until you’re ready to root the cutting.

Method 1 ~ Rooting In Water:
Once your stem is ready, place it in room temperature water. Keep your plant in a moderately bright spot, but not somewhere with direct sunlight. Don’t be alarmed if initially it starts drooping. Give it a day or two and it will perk back up.

Once the plant starts growing roots – which can take several weeks – transplant it into a pot with well draining soil. Keep the soil moist, but not soggy.

Method 2 ~ Rooting In Soil:
Using fresh potting soil, poke a hole in the soil’s surface and place your cutting inside. Then, firm the soil around it. You can also dip the end of the cutting in rooting hormone before placing it in the soil. This can help stimulate root growth.

Baby Scheffleras like humidity. You can create a tent of plastic over the plant to help keep in the moisture. Make sure the plastic isn’t touching the leaves directly. And remove the tent for a period of time each day to give the plant some fresh air. Alternatively, you can use a humidity dome and tray.

Keep your potting soil slightly moist. It’s very important the mixture doesn’t become too soggy or too dry. And, as with water rooting, place your growing Schefflera in a moderately bright spot with no direct sun.

New growth should be evident in a few weeks. Once you do, you can transplant your umbrella tree into a slightly larger pot.

A word about something you didn’t mention ~ Toxicity:
Schefflera plants develop calcium oxalate crystals which can be mildly toxic to people and animals, particularly when ingested. This basically is related to the S. arboricola variety, as the link below reveals. On rare occasions, some persons can develop a rash by handling the plant, so when pruning wearing gloves is advised.

You many benefit also from these links:
https://hortnews.extension.iastate.edu/faq/how-do-i-care-umbrella-tree
https://plants.ces.ncsu.edu/plants/schefflera-arboricola/
https://plants.ces.ncsu.edu/plants/schefflera-actinophylla/