I recently sold a holding and entered a transaction as such but the share has remained listed in my portfolio. Is that just that I have to delete it manually?
No - you shouldn't delete the position as all your transaction data will be deleted too ! If you want to hide these positions, there's an option at the bottom of the page on the right which you can click to hide any closed positions.
Some people do like to add stocks to their portfolios that they are thinking of buying before they purchase them. This checkbox allows flexibility to use the portfolio tool as you wish and review historic, current or future positions.