On a Chromebook, when you press CTRL+SHIFT+U in an input field, you’ll get a little underlined “u” on your screen.
Now, type in the unicode entry for the special character you want. An em dash is “2014.”
Hit enter and voila, em dash: —
A list of Unicode values can be found at these websites:
The Unicode entries for subscript are U+208X, where X is the number you want in subscript. For example, H₂0 uses CTRL+SHIFT+U and then 2082.
The Unicode entries for superscript are CTRL+SHIFT+U and then 207x, where X is the number you want in superscript. For example, 10⁷ uses CTRL+SHIFT+U and then 2077.
That is, except for 1, 2, and 3, which are CTRL+SHIFT+U and then 00B9, CTRL+SHIFT+U and then 00B2 and CTRL+SHIFT+U and then 00B3 respectively.
Use the handy table below for your accents, dashes and other esoteric punctuation.
(Open the table in sheets to see them all)