You should look at the Aggregation Data for Selection feature available in all grid's right-click menu.
More info in: http://confluence.dbvis.com/display/UG95/Viewing+Table+Data#ViewingTableData-AggregationDataforSelection
It shows a lot of data for the current selection including sum.
Thanks for the pointer.
Aggregation Data for Selection is very useful indeed. There is a reason, though, Excel and Aqua Data made Sum into an easily-accessible default - you see it right away without any additional clicks. Very convenient.
You can resize the window to your liking and keep it aside of the grid. It gives you a lot more details at hand while for example ADS only shows basic info.
I agree that it requires a click to popup the window but on the other hand it doesn't consume resources or raise attention unless wanted.
It would be great if DsVis show a sum of currently selected numeric cells in the results grid.
Similar to Excel or Aqua Data Studio. It's minor but surprisingly handy.
Bonus point for putting commas as the thousands separator in the sum.