I want to change the dropdown list of the module to be displayed in layouts

I am not a developer and hence using opencart to create my website. When I edit a layout, the dropdown list of the content is very limited. I want to include a custom dropdown parameter in this.

On the homepage, I want to display 1 of the category which I have created. When I edit the home layout, in the content dropdown list I see only Category under Category header. I want the list to display the categories created by me in this dropdown list. Example; I have a category called Interests. In the dropdown list under category I want the list to show the name of the category Interest. This will be irrespective the category is Parent or Child. How can I do that.

Sorry I think you're going to have to explain what you're trying to do a bit more clearly, I certainly couldn't figure it out.