@Rioscar-Orion-ghandy
I will assume you want the new line inserted after each and every instance of </Entry>.
Here is a solution using “Find and Replace”.
First, make sure you have a safe backup of the original file.
Next, use the backward P toolbar button (“Show all characters”), or, menu item View -> Show Symbol -> Show all chars, to view your file’s line endings. (You can show or unshow all chars whenever you want. It has no effect on the text in the file.)
Probably the line endings are CRLF. If they are LF then, in the solution below, instead of \r\n use \n. If they are something else, you will need to describe them, and an adjustment will be needed.
Invoke Replace dialog (Ctl+h)
Find what: </Entry>\r\n
Replace with: </Entry>\r\n<-------------------------------------------------->\r\n
In the group of four options on left side, first three UNChecked; 4th one ‘Wrap around’ should be checked.
Search mode: Extended
Now use Replace All to process the whole file, or, you can use Replace if you want to see how it works line by line. Ctl+z to undo.
Check the end of the file and decide if you want to keep the last inserted line.
Let us know if it worked the way you needed.