Solitaire Plus includes a smart-dragging™ feature that makes most moves automatically by simply clicking and slightly nudging a card (or stack of cards). The Help provides more detail about the feature and how it works.
In addition, the Options → Other panel provides a One-Click Moves option that triggers the smart-dragging feature by simply clicking a card. Smart-dragging with One-Click Moves is a great feature for MacBook users.
You can always override the automatic features by dragging the card (or pile of cards) over a specific target pile. The mouse cursor should pass over or through the pile you wish to target with the override.
Note: Double-clicks are not available as a shortcut when One-Click Moves is enabled since the move is made when you first click. You can use a right-button mouse click, or a two-finger tap, as an alternative to double-clicks.