Board view, and task views both offer this feature. But it is lacking from the list layout view.

Currently, you need to hover over the hotspot - click to activate dropdown- scroll to close tab - and click to enable.

Can it be reduced to something as indicated in the MS paint hack, so it is a one-click operation?

It might also pay to make the length/size of the hover hitbox bigger as it is a bit narrow. So when it slides out, you would then have both a one-click tick to complete button and the dropdown option if you want to move it to a different status.

The group select and modify is nice for bulk edits but lacks the ability to quickly snipe the completed tasks you have open and is less rewarding that knocking them down.