Hi -
A couple suggestions:
-
you can update to use the Segment Editor (in the latest release) and use it in place of the Editor and ModelMaker steps. (https://www.slicer.org/wiki/Documentation/4.10/Training#Segmentation)
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to automate things in Slicer you can use python scripting, which is very powerful and not too hard to learn (https://www.slicer.org/wiki/Documentation/Nightly/Developers/Python_scripting)
As for the extension catalog it should be available. Maybe these links will help you debug.
https://discourse.slicer.org/t/trouble-with-extension-manager/2457
Hope that helps.