I do (1) for
all traders (exporting, but import whole bins, because you can never
[Citation needed] have enough bins).
Empty bins show up differently from bins with things in, so after some horse-trading (albeit that
actual horses will be in cages...
) I tend to come back to non-trading mode, go into the Depot's "bring to depot" chooser and unmark the now empty bins just to keep the Trading list tidier (just loose items, and any further binned items indented from their bin that haven't been sold yet/hadn't been brought to depot/requested-to-be-brought during the prior time of haggling).
Though I tend to make pre-Depot (or indeed all) stockpiles mutually exclusive to wood/non-wood for items where this trivially applies (with a partner pile for the other subtype) and thus don't have mixed-heritage goods in a bin, if I did have wooden and metal bolts, or wooden and stone crafts, or whatever the mix, I'd be meticulously selling the non-wood indented items then de-mark-for-trading (and even mark for dumping, when I want to use that differently prioritised/service haulage-method) the bin and the wooden remnants. Also applies to other partial-intent mixes (wanted to leave marble trinkets for the dwarf caravan, happy to sell all metalic items but the iron and steel ones, ...) if not pre-arranged to be segregated.