Learn English – Abbreviation for “Master?”

all-acronyms.com states that "Quest" can be used as an abbreviation for "Questionnaire".

I have seen this used before, though the word "quest" has an entirely different meaning then questionnaire does, so I generally avoid trying to abbreviate the word so that there is no confusion.

But in the context that you are using it (in a figure), perhaps if you labeled it as "quest." it would be suitable.

When in doubt, spell it out.

As for general rules, Wikipedia has the following:

If the original word begins with a capital letter, so should the abbreviation. (ex. Volume = Vol.) If the original word begins in lowercase, capitalization is not needed.

The use of periods differs between British English and American English.

• In British English, according to Hart's Rules, the general rule is that abbreviations terminate with a full stop (period), whereas contractions do not.
  Doctor (contraction) = Dr
  Professor (abbreviation) = Prof.
  The Reverend (contraction or abbreviation) = Revd or Rev.
  The Right Honourable (contraction and abbreviation) = Rt Hon.

• In American English, the period is usually added if the abbreviation might otherwise be interpreted as a word, but some American writers choose not to use one.

To form the plural of an abbreviation, a number, or a capital letter used as a noun, simply add a lowercase s to the end. (ex. Mind your Ps and Qs.)

To indicate the plural of the abbreviation of a unit of measure, the same form is used as in the singular. (ex. 1 min or 20 min.)

Searching for "heat it in the mic" (in quotes) on Google comes up with a number of results, most of them of the forum/blog variety. I think this is evidence enough to show that mic is in use as an abbreviation for microwave, particularly (as you'd expect) in casual contexts.

As I've never heard it used before and have lived in many different US states, I'm inclined to say it's quite dialectical. Which dialect, though, I'm not sure.