The Song of Songs has this passage about windows:

behold, he standeth behind our wall, he looketh forth at the windows, shewing himself through the lattice.

(As an interesting aside: Jewish Priests bless their congregation making this sign with their hands. 

There is a lot of symbolism packed into this. The spaces or windows between the fingers represent the lattice through which God reveals Himself. 

The fingers form the shape of the letters shin, daleth and yod: ש  ד  י which spells Shaddai or Almighty. 

Also you can see how the fingers are divided into 28 segments to symbolize power.

(Leonard Nimoy, who grew up going to synagogue, borrowed this symbol for the Vulcan salute. So it looks a bit familiar but a bit strange in this context.)

This follows the pattern started by Aaron in Leviticus 9: 22

And Aaron lifted up his hand toward the people, and blessed them 

The blessing comes from Numbers 6

The LORD bless thee, and keep thee: The LORD make his face shine upon thee, and be gracious unto thee: The LORD lift up his countenance upon thee, and give thee peace.)

Back to the temple:

This window is in a sealing room. There is an identical window in the Celestial room.

See here for another symbol at the baptistry window.

Count the panels in that window. It is 9 high and 11 across. That is 99. What a unique number. Immediately, this calls to mind the Lord's parable of the lost sheep. "if a man have an hundred sheep, and one of them be gone astray, doth he not leave the ninety and nine, and goeth into the mountains, and seeketh that which is gone astray?"

I've heard it said that temple work is done one by one. We do not perform a baptism and read off a list of names. We do each ordinance one individual at a time.

Windows are a source of light. Of course windows do not generate light, but they transmit light. What a good symbol of ministering.

Depending on the circumstances sometimes windows allow light into the building and sometimes windows shine light from the building.