Many functions (e.g 'Delete' from the edit menu) require that you have selected some range of bars and tracks that will be affected by the selected operation. You can drag a rectangle to select a range. Holding the shift-key down while pressing the left mouse button will continue a selection. This way, you can select a range bigger than the window by continuing a selection after scrolling. Alternatively, you can click into the leftmost column to select a whole track.
The selection indicates a range of tracks (y-axis) and a range of bars (x-axis). These values are copied to the Event filter from Settings-Menu. In the event filter you can specify more precise, which events shall be worked with.
Example: To delete all events but program changes from bar 5 to 15 on track 1 to 3, mark bars and tracks by dragging a rectangle. Then select the event filter and disable program-changes (patch). Finally select Delete from Edit-Menu.
Figure 2.3: Selecting events