What part of oatmeal cookies are making them soft / chewy? I'd like to recreate the texture of an oatmeal cookie in very different flavor profiles, ie savory / umami. I'm tinkering with only the rolled oats for now, but I wonder if the chewiness could be coming from another ingredient, or a specific ingredient interaction during the cookie making process. For example, do I need creamed butter to achieve that texture or can I do without ?

To be clear I'm not looking for a cookie recipe, more like an analysis of how they come together. But if you have a recipe of a savory "oatmeal galette" or similar, I'll gladly take it. Thanks for your answers.
There are several ingredients and procedures that work together to determine the structure and texture of a cookie.  At the end of this recipe on ChefSteps, there is a very detailed explanation.  I am sure it is possible to make a savory version, you are just going to have to be creative in your approach.  If you search their site, they also have tips for making gluten free cookies more "cookie-like."  You might explore the use of different sugars, which have differing levels of sweetness.  You can shop Modernist Pantry, for example, as an online source of these ingredients.  

In direct response to your question, and according to the information in the link I provided, the following ingredients contribute to the texture of a cookie: sugars, butter (its temperature...and how they are mixed), liquid-to-flour ratio, temperature of the dough when it is baked, and whether or not you choose to compact them after baking...so, there are a lot of variables that you will need to experiment with.

Alternately, for savory applications, you could use a tuille.