To be done in "Video editing" mode.
One weird thing is, the video will be limited by the right bar, which needs to be moved further to the end of the video. However, it has no means of grabbing it. Instead in the bottom-right corner hidden "End" button. The trick is to click it and hold down while moving the mouse left or right.
Upon opening a video, the video track will appear at the bottom pane titled "sequencer". By moving blue line to one or another place and pressing K (split), you kind of split the track. Now, cutting the middle of a vide comes down to doing splits in two places, selecting the track in between the splits and pressing "delete". Then moving the right-hand side of the track to the left to join them together.
- Make sure the upper-right tab has the correct code, quality, etc; and also the output dir.
- At the top-left menu choose "Render → Render Animation". This should start encoding along with launching a window showing the currently rendered frame. The video inside this window will be lagging, but that won't have any influence on the final result, it's just this window.