It would be a useful feature to have an option and/or button that would allow to set and reset the current editor buffer/tab read-only state, something like in KDE's kate or vim.
It would be useful especially in the situations where multiple tabs are opened and worked on to avoid unwanted modifications to tabs containing valid code.
A few versions ago there was a plugin for such a feature, plugin that was discontinued unfortunately and I'm not aware of such feature to be available in the editor.