Tolong jemur handuk basah itu di balkon sebelum malam.

Indonesian imperatives (commands/requests) often omit the subject because it’s understood from context.
So Tolong jemur ... naturally means (You,) please dry .... Adding kamu can sound more direct/pointed, depending on tone and context.

Tolong is a common way to make a request more polite, similar to please. It can feel slightly more like help me by... / could you..., but in everyday use it’s often just please.
You’ll also see polite variants like Tolong ya, ... (a bit softer) or more formal Mohon ....

Yes. Jemur specifically means to sun-dry / air-dry by putting something out (often in the sun)—like laundry, towels, chilies, crackers, etc.
If you mean “dry” in a more general sense, you might use:

• keringkan = dry (make dry), often with a tool or method
• lap = wipe dry (with a cloth)

So jemur handuk is very natural for hanging a towel to dry.

In commands/requests, Indonesian commonly uses the base verb (without meN-).
So jemur! is the imperative/request form.
Menjemur is more typical in statements describing an action:

• Saya menjemur handuk. = I am drying the towel (by hanging it out).

• handuk = towel (noun)
• basah = wet (adjective describing handuk)
• itu = that (demonstrative)

It’s common for Indonesian demonstratives (ini/itu) to come after the noun phrase:

• handuk itu = that towel
• handuk basah itu = that wet towel

This is one of the big word-order differences from English.

They mean different things:

• handuk basah itu = that wet towel (identifying which towel)
• handuk itu basah = that towel is wet (a statement about its condition)
• itu handuk basah is possible but more like That is a wet towel (pointing something out), and it’s less likely in this request structure.

di marks location: in/on/at (depending on context).
So di balkon = on the balcony / at the balcony (English usually says on).

Di balkon is already natural for “on the balcony” (as a place). You only need extra words if you mean something more specific:

• di atas = on top of (physically on a surface)
• di luar = outside
  For hanging a towel, di balkon is perfectly normal.

Sebelum malam literally means before night (comes)—i.e., before it gets dark / before nighttime.
If you want to be clearer about “tonight” as an event/time later, you might hear:

• sebelum malam ini = before tonight
• sebelum nanti malam = before later tonight
  But sebelum malam is a common, natural shorthand in daily speech.

It’s a polite request, but sebelum malam adds a deadline, so it can feel more urgent than a simple request. Still, it’s not harsh because it starts with tolong.
Stronger/more direct would be just Jemur handuk basah itu... without tolong (depending on tone).

Both are common. Jemurkan (with -kan) can sound a bit more “do it for me / make it happen,” and it’s also very common in instructions:

• Tolong jemur handuk itu... = Please dry that towel...
• Tolong jemurkan handuk itu... = Please hang/dry that towel (for me)...

In many everyday contexts, the difference is subtle.

More casual (to a friend/family, depending on relationship):

• Jemur handuk basah itu di balkon sebelum malam, ya.

More formal/polite:

• Tolong jemurkan handuk basah itu di balkon sebelum malam, ya.
• Mohon jemurkan handuk basah itu di balkon sebelum malam. (more formal)