Swedenborg says that food in general — and bread in particular — represents the desire for good. This makes sense, since food gives us energy to do the work of being good, and the nutrients we need to build our bodies.
The manna given miraculously to the Children of Israel in the wilderness was, in essence, food given directly to people by the Lord. So it follows further that it represents the Lord’s presence inside us, and the desire for all things good that flows from that presence.
The exact nature or expression of that goodness depends on context. When the manna is first given in Exodus, the journey of the Israelites represents the development toward a truth-centered spiritual state, so the manna represents “the good of truth,” or the goodness that flows from knowing what is right and loving it because it is right. Other references refer to goodness at different levels, including the exalted state of those who live in pure love of the Lord.
Passages from Swedenborg
Apocalypse Explained (Whitehead) n. 146
146. To him that overcometh, to him will I give to eat of the hidden manna, signifies that those who conquer in temptations will have the delight of heavenly love from the Lord’s Divine Human. This is evident from the signification of “overcoming,” as being those who conquer in temptations (for it is these that are treated of in what is written to the angel of this church, see above, n. 130); from the signification of “giving to eat,” as being to be appropriated and to be conjoined by love and charity (see Arcana Coelestia, n. 2187, 2343, 3168, 3513, 5643) and as it is said “of the hidden manna,” which means the Lord in respect to His Divine Human, the “eating” of this here signifies the delight of heavenly love, for this is appropriated by the Lord’s Divine Human to those who receive Him in love and faith; also from the signification of the “hidden manna,” as being the Lord in respect to His Divine Human. That this is “manna” is manifest from the Lord’s own words in John:
Our fathers ate the manna in the wilderness, as it is written, He gave them bread out of heaven to eat. The bread of God is He who cometh down out of heaven, and giveth life unto the world. I am the bread of life. Your fathers did eat the manna in the wilderness, and they are dead. This is the bread which cometh down out of heaven, that a man may eat thereof and not die. I am the living bread which came down out of heaven; if any man eat of this bread he shall live forever. The bread that I will give is My flesh (John 6:31-58).
That it is the Lord Himself who is meant by “manna” and by “bread,” He plainly teaches, for He says, “I am the bread of life which came down out of heaven.” That it is the Lord in respect to the Divine Human, He also teaches when He says, “The bread that I will give is My flesh.”
Arcana Coelestia (Elliott) n. 8464
8464. ‘It is the bread which Jehovah has given you to eat’ means that this is the good that will become their own and constitute their life, in the highest sense that this is the Lord within you. This is clear from the meaning of ‘bread’ as celestial and spiritual good, and in the highest sense as the Lord, dealt with in 276, 680, 2165, 2177, 3464, 3478, 3735, 3813, 4211, 4217, 4735, 4976, 5915, at this point spiritual good, that is, good as it exists with a member of the spiritual Church, which is the good of truth, dealt with just above in 8458. Since that bread was the manna it follows that this good is meant by ‘the manna’. This is also made plain by the description of it in verse 31 of the present chapter, which says ‘it was like coriander seed, white, and its taste was like that of a cake with honey’, as well as from the description of it in Numbers 11,
The man[na] was like coriander seed, and its appearance like the appearance of bdellium. They ground it in mills or beat it in mortars, and cooked it in a pan, and made cakes out of it; and its taste was like the taste of fresh oil.* Num. 11:7, 8.
From the details given here it is evident that ‘manna’ in the spiritual sense means the good of truth, that is, good as it exists with the spiritual Church. They also explain why it is called ‘the grain of the heavens’ in David,
He commanded the skies from above, and threw open the doors of the heavens. And He caused man[na] to rain down onto them, and gave them the grain of the heavens. Ps. 78:23, 24.
‘The grain’ is the good of truth, see 5295, 5410. ‘Manna’ again stands for the good of truth, which is given to those who undergo temptations and overcome in them, in John,
He who overcomes, to him I will give some of the hidden manna to eat. And I will give him a white pebble. Rev. 2:17.
The fact that ‘manna’ in the highest sense is the Lord within us is clear from actual words used by the Lord in John,
Your fathers ate the manna in the wilderness, and they died. This is the bread which comes down from heaven, that anyone eating of it may not die. I am the living bread which came down from heaven. If anyone eats of this bread he will live forever. John 6:49-51, 58.
From these words it is clearly evident that ‘the manna’ in the highest sense means the Lord. The reason why is that ‘manna’ is the good of truth; but all good comes from the Lord, so that the Lord is within good and is Himself that good.
As regards that good, that this will become their own and constitute their life, this is meant by ‘eating’, 3168, 3513, 3596, 4745; for good which comes from the Lord brings the life of heaven to a person, and from then on nourishes and sustains it.