XLF Short tag view does not accurately reflect tag order and relationship between tags

In the short tag view placeable elements in the target text are consecutively numbered independently from placeable numbering in the source text.

This leads to the same placeable having different numbers in source and target text in the following two cases:

1. If the order of placeables has been changed during translation. (Indicated by the red arrows in the attached screenshot)
2. If a non-breaking space or another character that is treated as a placeable is inserted in the translation. (Indicated by the blue boxes in the screenshot)

The screenshot shows the same segment in full tag view and short tag view.

Apparently this has already been fixed once before (TRANSLATE-957), so this error likely due to the structure of xliff files created by Across.

The ph Tags in Across XLF files do contain an id attribute to which the numbering could be mapped.

Additional small issue:

Duplicating tags inside the edited target does not trigger the tag check anymore (only missing tags so far).