In informal settings like to family or close friends, this would okay to say. However, just as you said, in a more formal setting like in a restaurant, you wouldn't want to upset the chef/cook and so you would leave the sentence open so that what you are trying to say, is implied.

What does this mean?

In that sense, it would mean the same thing but in order to differentiate it, the sentence is written differently. Saying "This tea is bad" in comparison to "This is bad tea" is not the same as to how you are presenting the sentence. Regardless, the japanese sentence is literally saying Kono (this) ocha (tea) wa (particle) mazui (tastes bad) desu (to be) so it would have to translate into "This tea tastes bad."

Well, that would require you to write the japanese sentence differently.

これはまずいおちゃです。

I don't know if this construction has a grammatical name in English or Japanese, in the German course there were two ways of separating adjectives.

The predicative adjectives: Subject is/are adjective.

And the nominal adjectives: Subject1 is/are adjective+subject2 Or: Adjective1+Subject is/are adjective2

In German, and I think also in Japanese, the adjectives may change form according to this separation.

Any native that can clarify this? どういたしまして in advance.

Have a good day.

"This is bad tea" would probably be これはまずいお茶です. これ=this, まずい=bad, お茶=tea, です=is. However, I don't think it would matter which one you use in conversation, as they have the same meaning, just different wordings.

It's point to bad food/taste as I always noticed.

Here is a helpful lesson on the KSAD rule. http://www.japaneseprofessor.com/lessons/beginning/demonstratives-the-ko-so-a-do-series/

If u have watched jjba the antagonist dio says "kono dio da" which means "it was me dio" so i often think "this dio" because u refer to something close by. IK its a bad example but it help me

I remember kono close to me Sono so far away like when asking someone to hand u something not far but u r being lazy

Yes it's effectively this tea is digusting.

これ (kore) means this and it's independent pronoun, you use it to point at things

この (kono) means this thing, you can't use it alone, it's dependent pronoun, you always must put something with it

for example: kore wa nan desu ka?? what is this? - independent

kono ocha wa... this (thing) tea is... - dependent

That's how I understand it...

In my experience, hiragana is more common.

Then suggest them; that's what the flag button is for. And remember, the course is still in beta, so instead of berating the course developers, you might be better off having a go at other users for not flagging and suggesting enough alternatives for you.

Also, synonyms though some words may be, "bad", "disgusting", "gross", "undrinkable", etc. have subtly different nuances which don't necessarily correspond to the usage of まずい in Japanese. This is all a learning exercise, so maybe the course developers want you to learn some Japanese synonyms too, and that would be made easier by restricting the translation of one word to the one nearest English equivalent.

If you use it as an adverb,
A. That would mean that the tea is bad at tasting, and
B. The sentence would be ひどく味わいます.

Was just coming on here to post this. I'm not sure, but I think, "This tea tastes bad" seems incorrect / colloquial; I'd definitely say, "This tea tastes badly" in a translation if we were made to use the root-word "bad".

I put that as my answer and got it wrong, but I think it`s right.