what I had in mind for "edit with text editor" is not that I have file open for hours, but just quick edits.

Indeed. And that limits you a lot. Indices would be out of the question, which means you don't have performance.

SQL is a beast for my current task.
- will be slower, i think

Will be slower than what? A hand-rolled solution in Perl where you lock entire files, and dump the entire data structure on each modification?

for now the question is how to make EDITS of FLAT faster ? with perl ofcource :")

Lower your requirements.

Abigail