How to disable this sort of selection in the code editor

Help and Feedback Scripting Support
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#1

I don’t know how to explain this clearly, but does someone know how to fix/disable this kind of selection in the code editor?
a

If this post is in the wrong category, please, tell me so I can move it to the right one.

#2

Looks like Overtype mode, if so, simply press Insert to disable it.

#3

It works perfectly, tysm!

e