Yes, you can divide Salvia plants. Simply by using cuttings
1. To propagate take healthy cutting of well mature stem to a length of 10-15 cm and remove any flowers leaves from it.
2. Then dip bottom of the cutting in rooting hormone, and Place the 3/4 portion cutting into a small container with well-draining soil and water the cuttings.
3. Rooting will start within 1-2 week.
Note - For further details check the product description on nurserylive.com