The support ask me to send ECMerge configuration file, where can I find it?

It is located in the settings directory of ECMerge.

• If you use the "portable" (as in portable on a USB disk):
  it is located in a sub-directory called: "portable-settings" near the executable (inside the .app bundle for Mac OS X, just near ecmerge.exe for others)
• If you use the standard installation:
  it is located in your user profile. The easiest way to reach it is to run ECMerge, execute the menu item called Customize / Macros / Open folder of / Users, then go to the parent folder.

The file is named guimergeconfig.#.xml (where # is a number, the highest number is for the most recent version of ECMerge installed).