Thanks for your question and for the time you took to research existing support topics for an answer. I assume the old topic you referred to is this one:
Export / Import Att. Categories
I have done no further work on the export/import topic, but there may be a simpler solution to your needs. If you already have a custom taxonomy you can use it with MLA by checking the support box(es) in the Taxonomy Support section of the Settings/Media Library Assistant General tab. Have you been able to do that?
If you have enabled MLA support for your custom taxonomies you can copy terms assigned to an item from one taxonomy to another by defining an IPTC/EXIF mapping rule. For example, you can copy terms from the WordPress “Tags” taxonomy to the MLA “Att. Tags” taxonomy be entering template:([+terms:post_tag,array+]) in the “EXIF/Template Value” text box in the Att. Tags row of the Taxonomy term mapping section of the Settings/Media library Assistant IPTC/EXIF tab. You can use your custom taxonomy instead of “Tags”, of course. When you run the rule terms will be added to the Att. Tags taxonomy and assigned to the appropriate items. Once that’s done you could stop using the old taxonomy and use Att. Tags instead.
If you want to continue using the existing custom taxonomy but stop using the Enhanced Media Library plugin you can implement your own code to register the taxonomy. You can add code to your theme’s functions.php file or create a small custom plugin with the registration code. If that is of interest I can be more specific.
Let me know if either of the two suggestions I’ve made would work for your application. Any additional information you can give me would be helpful. I will leave this topic unresolved until I hear back from you. Thanks for your interest in MLA.
