When are 'all-' and 'manch-' singular or plural?

Question

I've just started learning German and one of the books I was reading explains that you can use various words like articles by using the endings of the article cases. My book just says:

this/these     dies- (close to speaker)
that/those     jen- (away from speaker)*
all            all- (singular or plural)
each, every    jed- (always singular)
which          welch-
some           manch- (almost always plural)
such           solch-

*Jener used relatively rarely in German, and instead of it one can use dieser (this/that, these/those)

Some of the restrictions of plurality make sense to me: jed- is always going to be singular because it is referring to the individuals e.g. jeder Baum means "every tree", but some of the others confuse me, namely all- and manch-.

I would have expected all- and manch- to always be plural because they are used to talk about many of something e.g. alle Bäume means "all trees". When are the singulars used?

Answer 1

Yes, in German the indefinite pronouns all and manch can be used in singular. The following examples show this.

all

• Ich wünsche dir alles Gute.
  ^{(I wish you all the best.)}
• Er besitzt alle Macht.
  ^{(He has all the power.)}

manch

• Ich träume manches Mal davon.
  ^{(I dream of it sometimes.)}
• So manch einer versteht micht nicht.
  ^{(Some people don't understand me.)}

At least the English all is also used with singular here. For some, I could not find a corresponding example.

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Addition: In the comments, a user insisted on an example with all undeclined. Even though this is not part of the original question, I am providing here a passage from DUDEN 9 (8^th ed., p. 43), partly translated with the help of DeepL:

all-:
…
6. all die Mühe / alle die Mühe – all meine Freunde / alle meine Freunde: In front of a noun with an article word all can be both declined and undeclined. […] In the singular, with masculine and neutral nouns, the undeclined form is common in all cases today: All der Fleiß war vergebens. All mein Zureden half nichts. Es bedurfte all meines Mutes. The undeclined form, on the other hand, is no longer needed: Wozu alles dieses Geschwätz (Lessing). With feminine nouns, in the nominative and accusative singular both possibilities are equally important (all / alle meine Arbeit), while in the genitive and dative the undeclared forms predominate (all dieser Arbeit war er überdrüssig; ich in all meiner Unschuld und Unwissenheit).

Answer 2

all-

• die allgemeine Schulpflicht
  general compulsory schooling
• das alljährliche Weihnachtsfest
  the annual Christmas festival
• der alleinige Herrscher
  the sole ruler
• der allseits bekannte Star
  the well-known star
• der allmächtige und allwissende Gott
  the almighty and omniscient God

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manch

• Manch einer, der vor der Versuchung flieht, hofft doch heimlich, dass sie ihn einholt.
• Someone who flees temptation secretly hopes that it will catch up with him.