Add new line after finding last string in a region

[Nigel11]

Hello

I have this input .txt file (a demo of it here, on a small scale) that after running the Python 3.6 code it should write in the input the following output (please see the output interleaved with #):

Output:
Noclue
*Title Test
12125
124125
asdas 1 1 1 1 
rthtr 1 1 1 1 
asdasf 1 1 1 1 
asfasf 1 1 1 1 
blabla 1 1 1 1 
#Expected "*Title Test2" here
124124124
*Title Dunno
12125
124125
12763125 1 1 1 1 
whatever 1 1 1 1
#Expected "*Title Dunno2" here
214142122

#and so on for thousands of them..

I have this code, that I have to adapt:

index = 0
insert = False
currentTitle = ""
testfile = open("test.txt","r")    
content = testfile.readlines()
finalContent = content
testfile.close()
# Should change the below line of code I guess to adapt
#titles = ["TitleX","TitleY","TitleZ"]   

for line in content:
    index = index + 1
    for title in titles:
        if line in title+"\n":    
            currentTitle = line
            print (line)
    if line == "1 1 1 1\n":
        insert = True
    if (insert == True) and (line != "1 1 1 1\n"):
        finalContent.insert(index-1, currentTitle[:6] + "2" + currentTitle[6:])
        insert = False

f = open("test.txt", "w")
finalContent = "".join(finalContent)
f.write(finalContent)
f.close()

Any help on how to adapt the above code to display the desired output would be more than appreciated!
Thanks!

[Larz60+]

1. read input line
   
2. write line to output
   
3. If this is target line, write new data
   
4. Continue loop at step 1 until finished, but eliminate step 3