You can enable/disable tag locking by selecting ‘Lock tags’ from the XML menu or by pressing F8.
When active, tag locking blocks access to tags and attributes while facilitating cursor navigation (the cursor will skip tags and entity references) and translating literal ‘&’, ‘<’ and ‘>’ to the relevant XML entity references.
The aim is to prevent inadvertent changes to the document structure while preserving the user’s freedom to enter, delete, select, cut, copy and paste text.
You may wish to choose a color scheme that supports tag locking by de-emphasizing tags.