Sometimes it is necessary to run the second version of Gimp with other parameters (see some options in the file New-instance-Gimp.bat) or in another graphic editor.
The solution to this problem is ShellOut.py
viewtopic.php?f=9&t=970

It's just a more extensive ShellOut.

Three plugins for Gimp-2.10 for opening layers in:
- Gimp "File -> Export to Gimp" (new-instance or with other parameters),
- Krita "File -> Export to Krita" (i mainly for CMYK),
https://krita.org/en/
- PaintdotNet "File -> Export to PaintdotNet" (i mainly for effects ~ > 700).
https://forums.getpaint.net/topic/15260-plugin-index/

You can use the xcf format to open layers in another graphic editor.
The limitation is that Gimp< 2.9, Krita, PaintdotNet do not open xcf files in version 11-xcf (with new layer modes) - so before export they will be converted to the old Mode: Normal-Legacy.

In case of Gimp-2.xx edit the file "plug-ins\Export_to_Gimp\New-instance-Gimp.bat" to give the correct path to bin/gimp-2.xx.exe.

For Windows, if you choose the "Edit bat file?" - YES - this file will open in Notepad2 (also attached).
To check the correctness of the settings - you can double click on the bat file to launch Gimp with your selected options.

For Linux, I can't test (I don't know if it's good - but I assumed in Gedit - line 76) so you can choose "Edit bat file?" - NO and edit manually in the selected text editor.

For the portable by Samj version it will not use the Preferences directory.
This will create a directory c:\Users\...your name...\.gimp-2.xx for Gimp < 2.9 or c:\Users\...your name...\AppData\Roaming\GIMP\2.xx for Gimp > 2.8.

Just a few minor notes:

- selecting any language for the newly opened Gimp works if it has the language set to:
Language: System Laguage.

- for Portable by Partha version - sample call:

works using the "portable" directory (you do not need to specify gimp.exe in the "bin" directory)

- PaintDotNet is a very interesting program but only for Windows.

- calling Krita and PaintDotNet does not require editing any file - just indicate the executable program in the plugin window.