Yes, this is easy enough and a real time saver as the number of sites you manage increases.
/etc/nginx/conf.d/ directory, create one or more '.conf' files with the reusable config snippets you need. For example, type
sudo nano /etc/nginx/conf.d/headers.conf and put your headers in the file. The default nginx.conf has a wildcard include directive at the bottom which will automatically pick these up.
If you have snippets that should only be used on some sites, delete the wildcard include directive from nginx.conf and selectively place new ones in your server blocks, one snippet per directive.
Here are some examples:
Don't forget to test your new rules
sudo nginx -t and then reload your config
sudo service nginx reload to apply the changes.