The idea with the “j-text” paragraph style in the template you downloaded is that this style is used as the basis for all styles. So, you’d dupe it, say, and then set your Japanese font, size, etc, along with any grep style you wish to apply. It sounds like you are applying the paragraph style with the composer somehow after you set up some other style for the grep style for the lining numbers. Would this approach help?

@Bob: Thanks for the link to the Adobe TechDoc. I was not aware of being able to make separate user on Mac (albeit with some caveats) and have not tried it. I simply have a separate boot volume for each language version, usually an external drive. This began with CS3, and it is a pain. Not sure if it's due to technical reasons, business reasons, or oversight (the latter being how it was presented to me as having happened in the first place with CS3…)

@pixel-bot: Glad to hear our template is working out. It really is the best way to do CJK typesetting in the English version, for now. Just please make sure there is a native speaker checking things in the workflow at some point!