sed cannot find special string such as tag

I have spent hours searching how to insert text above a specific line containing the only string tag </Engine> in railo tomcat server.xml file.

I have tried to escape with

sed -nr '/\<\/Engine\>/p' /opt/railo/tomcat/conf/server.xml

to find what line number this string is, but I always receive error messages.

My goal is to automatically insert the new host name information when I create a new user above the closing </Engine> tag as it will make it easier to maintain.

I am not good with text/string manipulation and I would really appreciate some help with this.

Thank you.