Kaldu hangat itu membuat sup sayur lebih enak.

In Indonesian, adjectives usually come after the noun they describe.

• kaldu hangat = warm broth
• sup sayur = vegetable soup

So the pattern is often:

• noun + adjective

This is different from English, where adjectives usually come before the noun.

Itu literally means that, but in sentences like this it often works a bit like the in English, depending on context.

So kaldu hangat itu can mean:

• that warm broth
• or the warm broth

It marks the noun phrase as something specific and identifiable. Indonesian does not have a direct equivalent of the, so words like itu often help show definiteness.

When itu modifies a noun phrase, it normally comes after the whole phrase, not immediately after the noun.

So:

• kaldu hangat itu = that warm broth
• not kaldu itu hangat if you mean one noun phrase

Compare:

• kaldu hangat itu = that warm broth
• kaldu itu hangat = the broth is warm

That second sentence is a different structure: itu modifies kaldu, and hangat becomes the predicate.

Here membuat means to make or to cause.

In this sentence, it means:

• makes the vegetable soup more delicious
• or causes the vegetable soup to taste better

Buat exists too, but it is more informal and can have different uses depending on context.
Membuat is the standard verb form.

The prefix mem- is a common verb-forming prefix in Indonesian.
So:

• buat = root
• membuat = to make

Lebih means more, so lebih enak means more delicious, tastier, or better tasting.

Indonesian usually forms comparatives with:

• lebih + adjective

Examples:

• lebih enak = more delicious / tastier
• lebih besar = bigger
• lebih hangat = warmer

Unlike English, Indonesian does not usually add endings like -er.

Enak is very common and slightly broader than just delicious.

For food, it can mean:

• delicious
• tasty
• good

Depending on context, it can also mean things like:

• pleasant
• comfortable
• nice

In this sentence, lebih enak is best understood as tastier or more delicious.

Indonesian often does not use a verb like is/are in simple statements.

For example:

• Sup itu enak = The soup is tasty
• literally closer to Soup that tasty

In your sentence, the main verb is already membuat, so no extra is is needed anywhere.

This is very normal in Indonesian.

Yes, sup sayur is a natural and common way to say vegetable soup.

It follows a common Indonesian pattern:

• head noun + describing noun

So:

• sup sayur = vegetable soup
• literally something like soup vegetable

You may also see sup sayuran in some contexts, but sup sayur is very common and natural.

The structure is:

• Kaldu hangat itu = subject
• membuat = verb
• sup sayur = object
• lebih enak = result/complement

So the sentence works like:

• [That warm broth] [makes] [vegetable soup] [more delicious].

A helpful way to understand it is:

• X membuat Y lebih Z
• X makes Y more Z

Examples:

• Obat itu membuat saya lebih baik. = That medicine makes me better.
• Gula membuat teh lebih manis. = Sugar makes tea sweeter.

Yes. Bikin is a very common informal alternative to membuat.

So:

• membuat = more standard / formal
• bikin = more casual / conversational

Both are natural, but in writing or careful speech, membuat is often preferred.

Yes, it can be omitted if you do not need to specify that/the warm broth.

Compare:

• Kaldu hangat itu membuat sup sayur lebih enak.
  = That/The warm broth makes the vegetable soup tastier.

• Kaldu hangat membuat sup sayur lebih enak.
  = Warm broth makes vegetable soup tastier.

Without itu, the phrase sounds more general.

Hangat means warm, while panas means hot.

So the choice depends on the intended temperature:

• kaldu hangat = warm broth
• kaldu panas = hot broth

If the original meaning is specifically warm broth, then hangat is the correct word.