How to add code to body in plugin?

Question

Vue.js

I'm still trying to solve a problem, part of which is in the question Why does the div NOT go beyond the parent div?
I want to make a plugin, which, according to the idea, should add a side with smilies to the body, and from the text field (contenteditable) already absolutely position the block with smilies to the right place
. Actually, the question is, how to add a component to the body from the plugin?