Endnote X9 Cite connected publication in one item

There is a problem that puzzles me already for decades. I realize that this problem is limited to the chemistry community.

The journals Angewandte Chemie and Angewandte Chemie International Edition are publishing the same article in German and English language and ask authors to cite the work in both journals as a back to back citation. The recommended style is:

Author1,Author2, Titel, Angewandte Chemie Int. Ed., Year , IssueInt., PagesInt.; Angewandte Chemie, Year , Issue, Pages

In addition the output style of Angewandte Journals asks for collating citiations in the text as “ranges of consecutive” (1, 2 or 1a-f) and separated in bibliography with ;

Both Journals unfortunately have different Issue numbers and different pages for the same published article in the respective journal, such that using alternative Journal names is not possible. Additionally, I can’t see a possibility to format text selectively in an additional field, such as one could use a never used field to add this information.

This said only “omitting the author list” in Bibliography > Author List" is not enough as it would result in: 

1a) Author1,Author2, Title, Angewandte Chemie Int. Ed., Year , IssueInt., PagesInt.; b) Angewandte Chemie, Year , Issue, Pages

Is there a possibility to further collate those two journals to cite them only in one citation item (here 1a only)?

All colleagues I asked are editing their bibliography manually after finalizing the list… But there has to be a cleverer solution…

No, I don’t think you can collate two citations into one (your last question), but I would try to create a new ref type to use just with articles published in these journals, and a matching bilbiography template.  You probably don’t need to use the journal fields, as you can just use the actual journal names.  Use the title and secondary title fields for the alternate title in German and English?  the hardest part is the field to contain the second set of page numbers, as it won’t automatically ajust from 121-31 to 121-131 (for example), if that is required by the style.  

On the citation in text front, you may need to use a unique custom field that is blank in all other ref types, to get the desired result, but I am not exactly clear on what that would need to look like.  Might be best to edit the primary citation, to add the missing info in the “suffix” field.