layer /ˈlejɚ/ verb
: to form or arrange parts or pieces of something on top of each other : to form or arrange (something) in layers**
step /ˈstɛp/ noun
[count] : one of a series of actions that are done to achieve something
[count] : a stage in a process
operation /ˌɑːpəˈreɪʃən/ noun
[count] : a set of planned actions for a particular purpose
[count] : a single action performed by a computer
Unless the vertical list of unique color-separated design elements is actually visibly labeled as something specific* in the UI or moved to a horizontal layout (please no), or an option to “sort by element color” vs “sort by design-software-layer” (maybe for the promised AI plugin?) is added, I think that plenty of people are going to continue to call them layers and plenty of others will call them steps or operations and all will be correct as far as the dictionary definitions of the words apply.
*“without a key, a map is just a drawing”