Just like when side bar is visible we are able to view files/folder, whether it is possible to pass custom list of items to this side bar which will have some options
Show custome clickable list in side bar
I’m not sure I understood correctly, but no, you cannot fill the sidebar through the API with custom items. You can only add folders to your project or enable showing currently open tabs.
I just came across phantom class in sublime API and also minihtml which provides dynamic runtime preview alongside.
I have mentioned the requirement in my above’s comment (image).
Whether it is possible to dynamically update this HTML body using phantom class and show values after getting from APIs in fixed(hidable) sidebar like structure?
Yes, you can display images and do basic formatting in phantoms and minihtml, which supports a subset of HTML and CSS for styling. See https://packagecontrol.io/packages/Debugger for an example of an interface using phantoms.