To create a limit order, you have to follow the next logic
Action
Result
Right-click above current price
Sell limit
Left-click under current price
Buy limit
The same you can do with the context menu.
Modify order
To change the price, you need to drag & drop the order size.
If you move the Sell limit order under the current price the application will execute this order as a limit by the market price. Vise versa for the Buy limit order.
Cancel order
Double-click on the order size or use hotkeys to cancel an order.