Arsthbt

I am trying to make a language for a fictional world and I am wondering how a species without vocal chords could communicate via written language

Chalk and slate, charcoal and wood, or clay or wax tablets. (At least to start.) They would have started by scratching characters into the dirt and painting on cave walls, but technological necessity would develop portable tools.

That said, there's a more portable mechanism yet that would likely evolve in parallel - sign language. If the creatures are unable to make any sounds, that doesn't necessitate a written language.

(It goes without saying that advances in writing technology would be adopted as it was developed.)

It may be 2-dimensional as well as 1-dimensional

Speech, sign languages and such transmit a single sign at a time, thus forcing the writing, which is secondary, to also form a sequence of signs that can be read one at a time.

A language made by different species that originates in a written form directly doesn't have to follow this restriction. It's likely to develop from the sights of the body language, and there several signs can be formed simultaneously by different body parts, each being as complex as human facial expressions.

If your species have brains adapted to read such complex poses, their writings will first capture the poses in something like parietal art. And it will get more abstract from that, to the level of modern ideographs or more. But no need may ever arise to linearize it.

So the words or sentences in the language may be based on a graph grammar instead of our conventional string grammars. Graph grammars are usually more powerful at the same level of rule types, a context-free one able to form sentences that only a context-dependent can make in pure one-dimensional text. So a writing that has never passed through speech form has a potential to be something drastically different from human speech and lead to a completely alien way of thinking.

A language could be developed in any manner that conveys information. Sound can be carried in other ways than using vocal cords. Clapping, snapping fingers, clicking claws, sign language. It might even develop from facial expressions.

A written language might be assumed to start from pictures such as hieroglyphics, but it could also be symbol based. For instance, if the language started from sign language, the written language may mimic the shapes of the sign language. If the language were based on the tapping of sticks together, the written language may somehow show the beat (like music for drums).

How the language is conveyed may bias the society toward being more mathematical (from rhythms) or being emotional tuned to each other if based on facial expressions.

While it doesn't have to, I see no reason to think that the technology couldn't follow the same path as our technology, assuming they have hands or something similar once a language is invented to manipulate tools the same way.

My understanding is that pictographs like hieroglyphics are developed before an alphabet takes form. Once the alphabet forms, your fictional species could use bioluminescence to communicate in a style similar to morse code. A certain sequence of blinks would represent a written letter. Certain colors could also express different emotions.

Writing developed from pictures to pictograms to ideograms. In a species with spoken language it can then move to phonetic scripts such as syllabaries and alphabets. But in a species that does not speak the next step would reasonably a featural script describing whatever method they used to communicate without writing.

What form that takes is really up to you. For sign language it would be stylized representations of the gestures. For color based communication, it would be just the colors. Or bunch of lines of different lengths corresponding to different possible colors. Which would also work for scent or radio based communication.