shell-script-to-add-new-line-to-existing-file

I have a scenario where i need to insert a line in file using shell script file content: names = [ "victor-${env}/appname", "steve-${env}/appname2", "test-${env}/appname3" ] there is a variable named 'appName' and value will be dynamic. NOW, i will have to insert in >>> ( "test2-${env}/$appName", ) to file in any line between '[]' Note: appName above is dynamic I have tried sed command but its not picking up the dynamic value. sed -i '5i /$appName' file expected file output: names = [ "victor-${env}/appname", "steve-${env}/appname2", "test2-${env}/$appName", "test-${env}/appname3" ]