In this dialog box only two of the shown settings are used.
For certain longsome operations, the program offers to run them in the background. If you have set the respective checkbox for an operation, you can revert the setting here.
This setting is used to display at the bottom bar of the program window, how much memory the BL Banking program currently consumes. This can be helpful to analyze errors in certain situations.
By default, double-clicking with the mouse performs the Open action, while a single mouse click performs the Select action. You can switch to single-click mode and optionally combine this with hovering for Select and the arrow keys for the Open action. The effect of this setting is limited, as most perspectives have internal settings for mouse operation.
Figure: Preferences - Windows settings