In my case is video FadeIN, FadeOUT

Tested in kdenlive version: 
- Win7 Pro sp1 64bit
  - Kdenlive-17.04.3-w64
  - Kdenlive-17.08.2-2-w64
  - Kdenlive-17.12.0-w64
Linux Mint 18.1 mate 64bit "serena"
  - kdenlive-17.08.1-x86_64.AppImage
  - kdenlive-17.12-x86_64.AppImage

About my video: 1280x720px 25fps MOV --> video fade-In-OUT

1) In only one video track "Video1" I insert two clips of a trim video: clip_01 (6 sec) + clip_02 (7sec).
2) Insert the effects "Fade from Black" (FFB) and "Fade to Black" (FTB) into start and end of the two clips: FFB=2sec, FTB=2sec.

This is a view in Timeline:
[<FFB>######<FTB>][<FFB>#######<FTB>]

2.1) In "Project Monitor" play is OK.
3) In Timeline select all: the two clips and effects
4) In "Library" tab I click on "Add Timeline Section To Library" icon, and insert the name: "seq1_fade-IN_fade-OUT"(.mlt).
5) In "Library" tab I click on "Add clip To Project" icon.
6) In "Project Bin" I see my sequence "seq1_fade-IN_fade-OUT.mlt" and drag and drop in Timeline.
7) In "Project Monitor" player I see only the "Fade from Black" and "Fade to Black" relative at first clip (clip_01);
 the second clip (clip_02) haven't fade.

This is a play:
[<FFB>######<FTB>][#######]

8) In a text editor I open the "seq1_fade-IN_fade-OUT.mlt" file by the Library folder and I try to read/understand.

/* ******************************************* */
/* *** SOURCE from Library  (part of file) *** */
/* ******************************************* */
<playlist id="playlist0">
  <entry producer="2_playlist3" in="0" out="149">
    <filter id="fade_to_black" in="99" out="149">             /* OK */
      <property name="start">1</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_to_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">2</property>
      <property name="end">0</property>
      <property name="kdenlive_info"></property>
    </filter>
    <filter id="fade_from_black" out="50">                    /* OK */
      <property name="start">0</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_from_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">3</property>
      <property name="end">1</property>
    </filter>
  </entry>
  <entry producer="producer0" in="0" out="174">
    <filter id="filter0" in="620" out="670">            /* MISTAKE_01 ??? */
      <property name="start">1</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_to_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">2</property>
      <property name="end">0</property>
      <property name="kdenlive_info"></property>
    </filter>
    <filter id="filter1" in="496" out="546">            /* MISTAKE_02 ??? */
      <property name="start">0</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_from_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">3</property>
      <property name="end">1</property>
      <property name="kdenlive_info"></property>
    </filter>
  </entry>
</playlist>

/* ************************************************************* */
/* *** MODIFIED with text editor by me and OK (part of file) *** */
/* ************************************************************* */
<playlist id="playlist0">
  <entry producer="2_playlist3" in="0" out="149">
    <filter id="fade_to_black" in="99" out="149">            /* OK */
      <property name="start">1</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_to_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">2</property>
      <property name="end">0</property>
      <property name="kdenlive_info"></property>
    </filter>
    <filter id="fade_from_black" out="50">                   /* OK */
      <property name="start">0</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_from_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">3</property>
      <property name="end">1</property>
    </filter>
  </entry>
  <entry producer="producer0" in="0" out="174">
    <filter id="fade_to_black" in="124" out="174">      /* MODIFIED by me */
      <property name="start">1</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_to_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">2</property>
      <property name="end">0</property>
      <property name="kdenlive_info"></property>
    </filter>
    <filter id="fade_from_black" out="50">             /* MODIFIED by me */
      <property name="start">0</property>
      <property name="mlt_service">brightness</property>
      <property name="kdenlive_id">fade_from_black</property>
      <property name="tag">brightness</property>
      <property name="kdenlive_ix">3</property>
      <property name="end">1</property>
      <property name="kdenlive_info"></property>
      </filter>
    </entry>
  </playlist>


9) After modified the file "seq1_fade-IN_fade-OUT.mlt" I used it in Timeline.
Now I can also expand the clip sequence; before with original Library clip I can't.

I don't know if these changes are align with the mlt/kdenlive code.
I hope it can be help developers to fix the issue.
Thanks so much.

It seems you import an MLT library. If yes this function is broken somewhere around version 16.12. It is re-implemented in the Refactoring version. 

If you like you can test with the current Kdenlive_Nightly_Appimage: https://binary-factory.kde.org/job/Kdenlive_Nightly_Appimage_Build/lastSuccessfulBuild/artifact/

(In reply to emohr from comment #2)
> It seems you import an MLT library. If yes this function is broken somewhere
> around version 16.12. It is re-implemented in the Refactoring version. 
> 
> If you like you can test with the current Kdenlive_Nightly_Appimage:
> https://binary-factory.kde.org/job/Kdenlive_Nightly_Appimage_Build/
> lastSuccessfulBuild/artifact/

Hi emohr,
thanks for the info. I used the Library features. I just tested it with "kdenlive-19.03.70-f5c88b4-x86_64.appimage" in LinuxMint-18.1-64bit and after some crash it works right. Then that issue can be closed if Davy Bartoloni or others users think so.
However, since february 2018 I am using another NLE, Cinelerra-gg for its performance and stability: https://www.cinelerra-gg.org/
Thank you!

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