The motion of selecting area has been improved. (v188.8.131.52)
Previously, when dragging over a timeline clip, the area was selected.
However, as receiving some comments that it was inconvenient to overlap with the clip moving motion, we changed the motion as follows.
[How to use 'Select area']
1. Click the button "Select area" on the Timeline toolbar. When you click it, the whole area of the clip is selected and shown.
2. Select the desired area.
3. When you click the split button, the following three buttons appear.
Just select the desired motion: Keep selected area only (Ctrl +T) / Delete selected area only (Ctrl + D) / Split (Ctrl + X)