You can gain this awesome sidebar on all of your browser-based Steam trades. Why awesome? For example, you could add 32 refined metal to the trade in only 4 clicks!
It shows a quick total count of items proposed for trade.
The "Accept!" button does the obvious but it also skips showing any of the warning messages. It does not and cannot be used to avoid the mobile confirmation if you are sending items.
There is also an optional auto-accept feature for trade offers that you open that were sent to you to deliver items without taking any.
The "Search" dropdown holds a fully customizable list of search terms and can instantly type them in the standard search box for you.
The "~" button is my favorite. It provides a complete set of keyboard navigation features for trades. Its odd label is because it has also made "~" a hotkey to grab focus for keyboard input just like opening the console in many games.
The "<<" and ">>" buttons are just easier to access clones of the previous and next page buttons.
The "+" button adds an item to the trade with only 1 click.
The unlabeled dialpad buttons at the bottom enable only 1 click to add an entire row or the whole page to the trade.
Also, there are a few general tweaks on those pages:
window.SlicerTraderSearcheslist in the script and add your most searched-for words.
window.SlicerTraderAutoAcceptTimervalue to the number of seconds you would like to delay before automatically accepting those item delivery offers.