For being more precise this feature just mutes the audio or the video clip on the timeline.
After you mute a clip it will continue to behave as it is a standard clip on the timeline you just can't playback it.

Tried the new disable feature and noticed that especially the disabled status icon next to a clip's title can be near to impossible to read. Please see also this screenshot, where the red forbidden icon blends in with the red title background next to it, thus becoming almost invisible:

Maybe a way to improve contrast for the icon could be to ensure it is always drawn on a neutral background, such as the standard window background. Also, changing the position of the status icon may help also, such as placing it next to the clip's begin.

I don't know what to say.
I have not any icon on the clip strip. I spent several minutes for understanding where the command for enabling and disabling was and then I thought Jean-Baptiste just added the disable status to the code.
Anyway, the icon on the strip is not a bad idea. I thought you inserted the command on the right-click menu and then you used some color modification for remembering to the user which clips were muted.
By the way, I saw that in the audio filter there is a mute filter for audio which does exactly what enable/disable feature does.
I guess that it's better to have a common behaviour for video, audio and groups.

It's in the Clip menu (but not in the context menu). See here for screenshots and description: http://thediveo-e.blogspot.com/2016/05/kdenlive-ui-disable-timeline.html

I'm sorry to say that though I updated this night to the latest git version I have not the command even in the Clip menu where I already searched.
I tried also to reset the app by removing all the config folders but still no menu voice appears. :(

Just added this day, so it won't be in the nightly until tomorrow. (There's a reason I compile directly from source, as Jean-Baptiste killed a lot of bugs I tripped on all the time during the 15.08-16.04 timeframe and I needed these fixes quickly in order to continue working on my projects; many kudos to JBM!!!)

Ok. Thanks a lot for your answer.

Looks great with good readability! Jean-Baptiste, once again many thanks for your work!

I finally tested the new feature.
My opinions are:

1. The action is performed on audio/video clip in "mixed" mode. It doesn't work on "strict" mode.
2. If I'm in any mode I can't perform the action on grouped clip (this is, I believe, why the enable/disable option doesn't work on "strict" mode. In this modality, I guess, audio/video are separated and the the parts of the clip are grouped)
3. Suggest it's better to put all the commands there are in the "Clip" menu also in the right-click contextual menu of the clip in the timeline.
4. The icon and the change of color is perfect!

I installed all the packages I still missed on my PC so now I can compile the source from the git clone: so, since now, I'll have no more to wait for PPA compiling.
I just tested the latest version you uploaded half an hour ago.
About the Enable/Disable clips on the timeline feature, I think we can consider it complete.
There is only a very small bug on the graphic side. It's so secondary that I suggest you to fix it only if it's easy and fast to code:

• When you disable the audio part of a video/audio clip, both if the audio and the video are still grouped or not, the clip instead of looks like an audio it takes the same look of the video disabled clips.

I guess that it can create confusion mostly in the "mixed" mode where you can put audio clips in video tracks too.

I tested the new fixes:

1. Now the aspect of the disabled audio part of the video/audio clip is perfect.
2. Actually, I liked the precedent behaviour for grouped clips. Before if I clicked on an audio/video clip on the timeline for disabling it I was able to disable audio and video simultaneously, same as it is now. But if I selected just the audio or the video I was able to disable just the part I want to also when the clips are still grouped (if I want just to mute the video or the audio it is useful this approach which allows you to perform it without ungrouping the clip). In a group of several clips I was able to disable just the clips I want. Of course, if I need to disable more clips simultaneously I can select more of them by keeping the Ctrl key pushed or by dragging a lasso around the group of clips (also if they are not grouped) I want.

Of course, also the approach you adopted has a sense and it's useful. I just believe that to disable part of the group without ungrouping it maybe could be better.

I guess that the change you made was suggested by me.
I apologize for that indication.
Actually, I understood which, I now believe, is better only after the test.
Anyway, I guess we can keep this feature the way it's now and decide later when we used this feature during some real editing sessions.
I'm sorry if I created confusion.

I checked on other main applications. The ones which have this feature actually behave as Kdenlive is doing now on the latest git version.
More in Kdenlive we have the mute filter just for the audio too.
I guess that you can move this feature in the done column.

Is there a reason why I can't disable certain clips? For instance, I can't disable clips with speed effect or image clips? Or am I doing something wrong here? I'm on latest git master.