Normal writing mode is indicated by blinking "|" on the end of text. It is default and You can see it in all text editors, including THIS one - on godotengine.org.
Godot has some keyboard shortcut, that activates different mode, indicated by blinking "_". This one is frustrating, as it does not push text when You enter new text inbetween strings. How do You turn it off ??? What is proffesional name of this mode ?? I could not find it in Godots engine settings and shortcuts. Please help, it happens to me much more often when coding shaders