Adding words to the end of the line?

I have a filegroup of random files. I want to add a word from the end of the line of all files to a certain section, which is the 4th line from the end. However, I was never able to do it. Is there anyone who can help?

Sample;

Xxxx xxx xxxxx 1.0 to Xxxx xxx xxxxx v1.0

Your question does not make any sense. Try explaining it clearly.

Reply to #2:

I even prepared an example, what is not understood?

What I want to do is position a certain word or letter where I want it.

If I need to re-example, it's like putting the letter "v" in the 4th part from the end of the sentence.

Reply to #3:
What was not understood was that your question made no sense whatsoever. The example you gave was so trivially simple that I could not believe that was all you required. Please try reading the documentation!

If all you want to do is really just to add the letter "v" three into the first position from the end of the string then it would make sense to look at the "Add" method and read the description in the User Guide!

Add: v
At index: 3
Backwards