- Drag and drop clips into Clip Window. Drag and drop from Clip Window into Timeline, into any of several tracks. The number of tracks be unlimited, and is selectable in Settings->Configure Kdenlive.
- Toggling between Select and Cut Tools is the main workflow action. Click on the clip, and press S or X for the respective tool.
- Invert an image - Timeline->Add Effect->Misc->Flippo
- Adding space at the beginning of an entire project once it's impractical to drag everything: use Spacer Tool - it drags everything by grouping the entire project. Make sure none of the tracks are locked - which prevents them from moving.
- Kdenlive Pan and Zoom
- Reverse clip direction - in the Project Bin (where you drag in all your clip files), right click, and select Reverse Clip. This will make a new reversed copy of the clip with .mlt extension.
- Shading out parts of the screen - View menu -> and activate the "Properties" panel. - https://youtu.be/4pkmNi_XU1s
- See video - 
For finding open-source soundtracks for your videos, see Open Source Soundtracks