In the previous versions of DBT, if you had set up a Template to default to Grade 1 or Grade 2 braille, it was possible for authors to change grade through the Layout: Translation Codes menu, or equivalent keystrokes.
From 10.6 four new codes have been introduced which can only be used by either inserting the codes into the "initial" Style in a template, or manually inserting the Codes into the actual document. This is intentional, and designed to prevent undesired changes
The two codes [g1l] and [g2l] (the last character is l as in Lima or lock) will work in the same way as the [g1] and [g2] Codes, but cannot be overridden in the usual way.
If it is essential to switch grades mid-document, you must manually insert either [g1u] (u as in unlock) or [g2u] at the appropriate place in the text.