Apple - Is there a Mac keyboard shortcut to "Select Current Line"?

To select an entire line of editable text, assuming a left justified language...

If the insertion point cursor is at the beginning of the line, press:

• Command–Shift–Right Arrow ⌘⇧➡

If the insertion point cursor is at the end of the line, press:

• Command–Shift–Left Arrow ⌘⇧⬅

If the insertion point cursor is at any other part of the line, press:

• Command–Left Arrow, Command–Shift–Right Arrow ⌘⬅ ⌘⇧➡

  Note that in this previous key sequence set, that you can keep the ⌘ key pressed while pressing/releasing ⬅ then press ⇧➡ so as to eliminate pressing/releasing the ⌘ key twice.

See the Document shortcuts section in Mac keyboard shortcuts.

To move the cursor to the start/end of the line, you can use ⌘← and ⌘→.

To select whilst moving the cursor, add ⇧. You need to move the cursor to one end of the line first using ⌘← or ⌘→, then hold ⇧ and use the opposite ⌘→ or ⌘←.