The InDesign (*.idml) filter needs a mechanism for translators to specify the sort order of index markers by adding <so> tags. QuickInsert --> Insert Tag --> Index entry sort order (Apply sort order to index entry) is currently not available to add <so> and </so> tags for InDesign IDML. This functionality is most important when translating into Japanese as the translations of the index entries must sort according to a different alphabet (yomi) than the text that displays in the generated Index. Customized sort order could apply to other languages as well. This function is available for Framemaker MIF files.

See attached Trados Studio project with sample InDesign file with index markers. Note that two of the index markers have sort order in the source file as examples, but usually English source segments wouldn't have sort order. For a Japanese translation, many of the target index markers would require sort order tags and yomi translations added between <so> tags. /cfs-file/__key/telligent-ideas/c517502d-7e6a-4209-8cfc-0a1cea1966f4/test_2D00_index_2D00_markers.zip 

This is an example of how an index marker with sort order (Sort by) appears in InDesign. /resized-image/__size/1800x1200/__key/telligent-ideas/c517502d-7e6a-4209-8cfc-0a1cea1966f4/index-marker-with-sort-order-in-InDesign.png

This is how to access index markers in InDesign: Window --> Type & Tables --> Index --> double-click markers under letter headings: /resized-image/__size/1800x1200/__key/telligent-ideas/c517502d-7e6a-4209-8cfc-0a1cea1966f4/access-index-markers-in-InDesign.png