Separate+ was originally made for Gimp 2.4 - not maintained - not going to work as intended in Gimp 2.10
There is another application that can be used with Gimp 2.10
Cyan https://cyan.fxarena.net This can be used as both stand-alone application and with a Gimp plugin. The plugin installs first time you run Cyan.
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Edit: There is a new version (version 2) of CYAN that is stand-alone and does not work with Gimp.
Version 1.2 is the one for Gimp see:https://github.com/rodlie/cyan/tree/1.2 for downloads.
Edit: Windows users need an updated version not on the site: Get it from
https://u.pcloud.link/publink/show?code=...WoCJE51Jfk (11 MB zip file)
or the original from https://sourceforge.net/projects/prepress/files/1.2.1/ Note, this is a 7z archive
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This version is very new, bound to be some bugs, if you find one, do not tell me, tell the Cyan developer.
This a short video on use in Win10 & Gimp 2.10.8
direct link https://youtu.be/1A0Aaoy1mhQ duration about 4 minutes.
There is another application that can be used with Gimp 2.10
Cyan https://cyan.fxarena.net This can be used as both stand-alone application and with a Gimp plugin. The plugin installs first time you run Cyan.
-----------------------------
Edit: There is a new version (version 2) of CYAN that is stand-alone and does not work with Gimp.
Version 1.2 is the one for Gimp see:
Edit: Windows users need an updated version not on the site: Get it from
https://u.pcloud.link/publink/show?code=...WoCJE51Jfk (11 MB zip file)
or the original from https://sourceforge.net/projects/prepress/files/1.2.1/ Note, this is a 7z archive
-----------------------------
This version is very new, bound to be some bugs, if you find one, do not tell me, tell the Cyan developer.
This a short video on use in Win10 & Gimp 2.10.8
direct link https://youtu.be/1A0Aaoy1mhQ duration about 4 minutes.