can I use it only on one of my templates

For instance, if there would be one shortcode to show this warning on specific templates I wish?

There is no short-code for this plugin, it hooks directly into a few different places, and achieving that with a short-code would require refactoring it a bit.

However, you could use this filter https://github.com/JayWood/content-warning-v3/wiki/Dev-Documentation#hide-the-dialog-on-certain-pages-regardless-of-cookies

By setting the plugin to site-wide, and returning false in this filter you can essentially show the dialog where you want.