When trading, I generally use the ‘Overview’ screen. That shows the account positions with the quantity held. Anything I want to trade, I then enter the symbol in the right Buy/Sell section. By hovering the mouse over the small “i” next to 'Market Price" the last trade, bid, and ask are displayed. I then use that to inform the price to enter for the trade.
As suggested all the information could be laid out a bit better with current bid/ask AND the quantity of the security you are holding. Good suggestion! Alpaca will be doing a major overhaul of the web interface in the near future and I’ve put that on a requested feature list.