The “index” Code Block to insert a string Before another string is simply [ 0; ] but How would I insert a string AFTER another string that might be of various lengths?
I would try splitting your string at the known substring. Inserting the new string after it (in the list). Then concatenating them back together.
If you’re always using the same strings you can just replace the substring as well.
String1+String2; should do the trick. If not the question isn’t clear so some illustrations and a data set may be required.