How do I manage file lines in Python 3.10 (or newer)

No, it's not possible, unless you go via memory in one way or another.

Let me explain why: A text file is not line based - it's a binary file that is processed by applications which interpret the binary values as printable and unprintable characters. In the first class are the letters, number, punctuation, special characters (and in Unicode files an enormous number of other characters and language character sets).
And in the unprintable characters are some which the app to interprets as an "end of line character".

So when you try to insert or delete lines in a file, you can't because files don't "know" about lines. The only ways to do it are to read the whole file into memory, modify the memory, and write it back - or read it line by line and write it out to a new file line by line, adding and removing lines as you go through by writing extras to the new file for an "insert", or not writing them at all for a "delete". When you have copied the file over, you can then close them both, delete the original, and rename the new version.