Its not a Philodendron It is an Epipremnum cultivar called Neon.
The reason it has a blank space in the pot is because when these hanging baskets are put together by the grower they stick a few cuttings into the same pot so that there are more stems otherwise it would be just one, so each 'strand' of leaves in your pot is a separate plant.
Your plant will not get 'leggy'. When planted this way, this plant will only drape and grow down like it is now.
If you want to change that and have substantially bigger leaves you have to train it to grow UP on a totem.
You can cut pieces off the ends of your strands, making certain you get some nodes that have little roots, and just stick them into the black space in the pot. These root easily. But your plant should really be allowed to grow longer before you do that
