It's easy to see why a person who is a performer, artist, author, chef, or a bunch of other professions needs to schedule space and time to support their creativity. If they aren't producing work that is new, innovative, and directly tied to their creative voice and vision, they're not doing their job.
It can be harder to see how it's important in grad school to have a creative outlet. Although it can vary a bit from field to field, many grad students eventually come to feel that they're in a cycle of:
Obtain information
Write information down
Revise information
Share information
Repeat
But when you feel like you're just following a script, producing and sharing information without any real spark of interest, it can be a total slog! And more than that, it can feel actively unproductive to incorporate creativity directly or indirectly into your day because it isn't "useful" or "efficient". Put another way - what does coloring have to do with my dissertation?
Creativity is hard to define and can be difficult to research but there are lots of studies that attest to the fact that:
Creativity is linked to improved problem solving
Creative play can reduce stress
Creative activities activate different neural pathways in the brain
Creativity can boost self-confidence
So, to that end, there are a few things you can do right now to promote a little more creativity in your days!
Recognize that writing, even non-fiction, academic writing, is itself a creative act. You're choosing words out of an infinite range of possible words to communicate something that is only living in your brain! What might make it feel more creative? I like to sometimes practice writing my ideas in a different voice - more formal, the most jargon-y I can do, like I was explaining it to a 8 year old - to see if that clarifies my ideas.
Try representing your argument with pictures, or sounds. One of my favorite ways to do this is to make fake slides for a class I would teach on this argument, or for a conference paper version. Sometimes playing in a more visual medium can help you unblock!
Dictate your argument to your computer, or phone. Sometimes speaking more naturally, or recording a conversation you have with a friend about your work, can loosen up some stickiness.
Add some non-work related creativity into your routine! Knitting, coloring, sewing, doodling, bullet journaling, dance, acting, improv, creative writing, poetry, performance, cooking, cake decorating....the options are endless! But just because it doesn't a) make you money or b) move the dissertation forward doesn't mean it isn't worthwhile! Creative play and expression benefits don't diminish just because they don't serve the project directly!