Different combinations of せっかく, their meanings and examples

Question

As of today, the vast majority of times I've come across せっかく, I've ended up understanding it in a somewhat blurry way and guessing the meaning from context. However, I would like to finally structure my knowledge about せっかく in my head, so I have tried to classify the different combinations of せっかく that I have come across so far by groups according to their meaning (in each group I have tried to put those combinations with the same meaning that are interchangeable with each other).

Group 1

・ せっかく (just this word, with no any particular combination)

Meaning: according to dictionary, it conveys the idea of "with much effort". I don't know if せっかく can be used by its own, without forming any particular combination like the ones in the next groups. If so, I would really like to see an example.

Group 2

・ せっかくの + Noun

Meaning: one-time thing (ex. "one-time opportunity") / rare, valuable thing I don't know if it can mean other things as well.

Group 3

・ せっかくの～だから

・ せっかくの～だし

Meaning: since it is a rare ocassion, ...

Group 4

・ せっかく ＋ 普通形 ＋ Noun

Meaning: something that has taken a lot of effort to make

Group 5

・ せっかくだから

・ せっかくなので

・ せっかくだし

Meaning: since you have done a lot of effort in doing something, I accept.

Group 6

・ せっかくだが

・ せっかくだけど

・ せっかくだけれども

Meaning: I'm sorry that you have done a lot of effort in doing something, but I refuse.

Group 7

・ せっかく～から

・ せっかく～のだから

・ せっかく～んだから

・ せっかく～し

・ せっかく～のだし

・ せっかく～んだし

・ せっかく～ので

・ せっかく～からには

Meaning: since something will be done or has been done, ...

Group 8

・ せっかく～のだったら

・ せっかく～（の）なら

Meaning: since you are going to do something, you could do also...

Group 9

・ せっかく～が

・ せっかく～けど

・ せっかく～けれども

・ せっかく～のに

Meaning: just when something was done, ... (something negative)

Group 10

・ せっかく～ても／でも

Meaning: although you have done a lot of effort in doing something, ...

Group 11

・ せっかく～（んだ）もの／（んだ）もん

Meaning: it adds emphasis to something

The problem is:

1. I don't know if all these combinations are correct (some of them are written by deduction).
2. I don't know if all combinations are well-grouped.
3. I don't know if in each group there are other possible combinations that I haven't listed or if there are missing groups.
4. in some cases I don't know the exact meaning and in others I don't know if the meaning attributed to each group is correct or if there are missing meanings.

Therefore, I would greatly appreciate if you could help me.

Finally, if for each group you could please give me an example where I can see the meaning of せっかく that represents that group, it would help me a lot as well.

Thank you very much in advance for all of your help and sorry for the trouble.

Answer 1

Interestingly, 明鏡国語辞典 (3rd ed.) gives only one definition for this word:

せっかく

［名・副］ある物事や行為が、大きな価値をもっているという話し手の気持ちを、その価値が有効に生かされたかどうかの観点からいう語。

「ａ せっかくの御厚意ですからお受けしましょう／ ｂ これではせっかくの景観が台無しだ」
「ｃ せっかく帰郷したのだから、しばらく滞在なさい／ ｄ せっかくおいで頂いたのに何のもてなしもできません」
「ｅ せっかくですから、頂戴致します／ ｆ せっかくだが先約がある」

使い方
⑴「せっかくの…」の形で価値の内容を体言で示す場合（ａｂ）、「せっかく…のだから」「せっかく…のに」などの形で価値の内容を用言で示す場合（ｃｄ）、「せっかくだから」「せっかくだが」などの形で価値の内容を文脈で示す場合（ｅｆ）がある。
⑵その価値が有効に生かされる場合は、原因・理由を説明する順接表現となり（ａｃｅ）、生かされなかった場合は、多く無念や遺憾などの気持ちを暗示する逆接表現となる（ｂｄｆ）。

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• せっかく is fundamentally a word to express that something has (or had) an important value one needs to take advantage of. The valuable thing can be either a tangible thing, such as a gift, or an intangible thing such as an event, favor, trouble (as in "you took the trouble to ..."), offer, effort, or opportunity. The focus is on whether the "value" associated with the thing is successfully utilized.
• Syntactically, せっかく can work either as a no-adjective (せっかくの～ (a, b), せっかくだから (e), せっかくだけど (f)) or as an adverb (せっかく～したので (c), せっかく～したのに (d)). (You cannot say せっかくに.)
• せっかく can be linked either "sequentially" (a, c, e; 順接; e.g., から, ので, だし) or "inversely" (b, d, f; 逆接; e.g., けど, が, のに). When 順接-linked, せっかく has a connotation like "let's make use of the value", "let's take this opportunity", "let's not waste it" or such. When 逆接-linked, せっかく expresses a regrettable feeling of "failing to make use of the value", "missing the opportunity", "it's a waste", etc.

I don't think your grouping is wrong, but I feel it is already fragmentary, and there may be no point in expanding or completing this list. For example, you seem to have associated せっかくだけど with an "effort", but that is not always the case, and it can be used for various things that should not be wasted. In my opinion, it's more important to understand the underlying meaning of せっかく. The various translations on jisho.org are examples of expressing this nuance in English, but they don't mean せっかく itself has different meanings as a Japanese word.

Related: What's the difference between せっかく and わざわざ?

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EDIT: If I were to pick just one English word closest to せっかく, it would be "precious(ly)" or maybe "special(ly)". せっかく can be used outside contexts related to someone's effort, so "with much effort" is clearly too narrow a translation. Unsurprisingly, 明鏡's definition mentions nothing related to effort.

• せっかくです: (This event/chance/offer/suggestion/effort/etc) is precious (so let's not waste it).
• せっかくだから: This (event/chance/offer/suggestion/effort/etc) is precious, so...
• せっかくだけど: (I know this event/chance/offer/suggestion/effort/etc) is precious, but...
• せっかくの雪だから外に出よう: Since it's snowing (which is precious), let's go outside.
• せっかくの夏休みなのに勉強している: It's (precious) summer vacation, but I'm studying.
• せっかく夏休みが来たのに勉強している: The summer vacation has come (which is precious), but I'm studying.
• せっかく書いたなら読ませて: Now that you've written it (which is a precious occasion), let me read it.
• せっかく気持ちよく寝てたのに！: I was having a comfortabe sleep (which is precious)!