Another suggestion:
Since even boolean values in JS are still numeric, instead of "locking" items from selling at the market, allow locking "Count X" items (with 0 meaning "none", -1 meaning "all", and possibly a negative number less than -1 meaning meaning "All but the last N"). This way, players can do things like "Sell all but 10 locked items". It would also be handy to be able to sell multiple, such as "Sell 10 of everything".