How do I view my sequence in blocks of 3 or 10 nucleotides?
Viewing in blocks of 3 or 10 is available in SnapGene version 5.3 and later.
In Sequence view, click the "Use an alternative format" button in the side toolbar to choose to display the sequence in "Blocks or 10" or "Blocks of 3".
Note that "Blocks of 3" format starts from position 1 of a sequence and so will not necessarily align with the codons of translated features or ORF's. To ensure codons align with blocks of 3, consider extracting the CDS to a new sequence - see Extract a Region in a Sequence to a New File