How to change filename titles??

Found only one post on this topic and it didn’t go into enough detail so let’s try this again.

The “index.php” file in my theme shows up on my theme edit sidebar as “Main Index Template”.

My “posts.php” file shows up as “posts.php”.

All I’m trying to figure out is how to edit the filename that is displayed in my theme edit area sidebar so it says what I want it to.

The post I found/mentioned above said something about changing the commented out text in the file itself, but there is no commented text in the filename itself!

All I’m trying to do is make posts.php appear as Posts.

If you know how to do this please show me the code to copy/paste into the file and I can take it from there. Thanks!