A few beginner's questions

Hello @Nato ,
thank you for your message!
Yes, I also have an application to rename files, it’s a very good idea.
And to tell the truth, even the finder can do it, I realize.

What’s curious is that while searching in the Obsidian forums about this topic (for example here: Allow reading & writing .txt files as well as .md, I started to think (and to fear!) that changing the extension of notes from .txt to .md was risky or controversial.

But maybe it’s actually quite simple.
Let’s hope so, because I’m going to get a lot of them.
There will certainly be some formatting accidents, but not too serious I hope! The idea of making a backup is precious…

Strangely, I didn’t have any more problems with code blocks when I indent, I don’t know why and I don’t know what I did exactly the very first time.
I noticed however that when I ident text, the folding / toggle is visible and clickable in edit mode, but not in preview mode where it disappears, contrary to what happens with headers, i was surprised.

Something else I noticed:
I created a folder structure.
But when I create a new note, if the folders are closed, or if I’ve “wandered” from folder to folder, I don’t know where it will go. I’ve seen that there is a setting to specify a specific folder. But isn’t it possible to select a folder, and to create the note in this open folder (not with a right click on the folder title, which works, but with the “new note” button or with the “new note” shortcut)?