I have 2 video-tracks from 2 camcorders with a different angle, which have been synced using a flash. With 1 video-recording audio has been split to an own audio-track, which has been disabled.

So I have
1 combined track: video+audio (track1)
1 track with video only (track2)
1 disabled audio track (track3)

track1+2 have been grouped

So as a 1st step to understand how it works, I want to see both video-tracks in the project monitor at the same time. I understand that this useless.

As a 2nd step I would like to blend from 1 track to the 2nd and blend it back after a minute.

Link to tutorials are welcome.

The project monitor displays how your project is going to look when you finish and render it. So if you want both tracks to display on it then you need to add an affine or composite transition to create a composite that has both tracks. Use a the Pan and Zoom effect from the crop and transform group of effects to shrink and position the tracks in the frame.

To blend from one track to another add a transition.

You are pretty much asking how to use the basic functionality of this tool.
I suggest you use the quick start tutorial on http://userbase.kde.org/Kdenlive/Manual/QuickStart

Basics.

There is video how easy you can put two cams in the same time. Need to use Composite transition and Crop, Scale and Position effect. You can obtain any result like: PIP, or split vertically, horizontally... or other you want

- https://www.youtube.com/watch?v=3wevBe5mySw
- final: https://www.youtube.com/watch?v=s0ZWIcTEJMA

If you want to play audio from one clip, just exclude audio from clips, ungroup and remove one. Next edit your audio on audio path.

pinguin_drupal wrote:I want to see both video-tracks in the project monitor at the same time.

Split View

I want to see both video-tracks in the project monitor at the same time.

Like a I said before. You can't do this unless you create a project that has both clips in it.
The PROJECT monitor previews your project which is what your finished product is going to look like.
Above posts give you guidance on how to do that.

Whoops - my bad. I just visited the link to the "Split view" in the manual and found that yes you can see all the tracks at once in the project monitor.

And the really bad/embarassing thing is - the picture in the manual showing the split view is of my dog! Ie I wrote that bit of the manual !!

Really sorry Alastair. My reply above was a bit rude.

It is great feature to capture to a HDD big drive and use the Linux SSD drive to store the proxy, SSD can playback four proxy simultaneously without drop frames in split view.

I would love to have a multicam cut by pressing numbers in keyboard. It is awesome to have four clips playback in split view. I set the monitor window to 960x540 and use proxy size 480x270 and I get four clips playback simultaneously in a quad core machine without drop frames.

Realtime cut pressing 1, 2, 3, 4 keys in keyboard would be amazing!