Crossword patterns
A crossword gives you a length and a few crossing letters. Type the pattern with ? for each unknown: C?A?E finds CHASE, CRANE, CRATE, CHAFE and the rest. The pattern sets the length automatically. Add "contains" or "ends with" when the clue hints at a suffix.
Scrabble hooks and extensions
"Ends with" plus a length finds front hooks and back hooks: every 4-letter word ending in AT, every 8-letter word starting with UN. "Contains" with a two-letter string finds words that play through a pair already on the board.
Spelling bee and letter-restricted puzzles
For games that require a center letter, put it in "contains" and use the unscrambler with the seven allowed letters repeated (type each letter three or four times so the solver can reuse them).