Spend money: Auto-populate the amount by sum of detail line(s)

Hello, I am very new to essentials and immediately I see that there is no running total when creating a bill, or spending money:

When creating a new bill, the total amount appears in the top line of allocations, as taken from the invoice itself. If I then want to allocate the amount to separate accounts - for example, some is spent on GST products and other portions on non GST products and then still other portions on cleaning products, etc, I should be able to allocate the first two amounts manually and then there should automatically be an amount left which I can easily allocate to cleaning, rather than having to open calculator (inbuilt calculator sorely missed form accountright by the way) and work out how much is left to be allocated for cleaning. AS well as that, there is no amount on top of the bill itself, so I have to enlarge the invoice to see how much it was originally for, then delete the GST and non GST portions from that amount to arrive at the cleaning amount. Longwinded and frustrating.

Same goes for spend money. As in accountright, I should be able to enter the amount to spend at the top and then have a running deduction as I allocate to different accounts, finally arriving at a remaining account for the last amount to be allocated. I am so tempted to go back to accountright just because of this, and I have only entered one bill!