[SOLVED] Sed to replace range of text at specific coordinates

Hello everyone,

I wish to edit a document, replacing a range of characters with another range of text.
For example the following input has to be modified between character 3 and 7 with "1234".

Input:
Quote:

abcdefghijklmnopqrstuvwxyz

Output:
Quote:

ab1234hijklmnopqrstuvwxyz

I was thinking about using the command sed to do so, but it seems it only replace lines by ranges addresses, and not characters. https://www.gnu.org/software/sed/man...ange-Addresses

Would anyone know how to do the substitution?