You are now in Transcript Edit Mode

Click any word to select it

Edit the selected word (alternatively press K) (then type new spelling and tap when done)

Select the next word (alternatively press L)
Back to previous word (alternatively press J)

Restart playback from the selected word

Of course, the usual keyboard shortcuts still work also:
'Space' — Play/pause
'P' — Play/pause
'←' (left arrow) — Jump back by 30 seconds
'→' — Jump forwards by 30 seconds

For power users:
C — Add a comma at the end of selected word
O —Add a . (full stop) at the end of selected word
;  — Add a ; (semi-colon) at the end of selected word
:  — Add a : (colon) at the end of selected word
? — Add a ? (question mark) at the end of selected word
-  — Add a — (long dash) after the current word
A — Convert word to ALL CAPS
T — Convert word to Title Case (First Letter Capitalised)
S — Convert word to small letters (no letter capitalised)
D — delete a word [requires confirmation] (caution: no undo!)
Q — Delete a word without confirmation (caution: no undo!)

I'm done editing