Dummy Image Segments
With the File | New command you have the option to conveniently create dummy/makeshift segments for .e01 evidence files that can substitute missing/lost/corrupt original segments. The user specifies the required chunk size and the number of chunks as well as a filename for the desired segment (must be with the correct extension, identifying the segment number, not number 1). The data written into the chunks is a recurring textual pattern ("MISSING IMAGE FILE SEGMENT!" when running X-Ways Forensics in English), so that you know that you are looking at a gap in between available data when browsing the interpreted combined image later. The idea of such an artificial dummy segment is that if correctly created it can serve as a placeholder that ensures that data in subsequent segments has the correct logical distance from the data in preceding segmented. Of course, the hash of the entire image cannot be successfully verified any more if the original data is not present, and of course, this functionality should be used only as a last resort if there is no backup of the missing segment file and if data recovery fails etc., and creation and usage of such a dummy image file segment should be properly documented. (forensic license only)
When interpreting an .e01 evidence file that contains dummy segments, you will be notified, and the total number of placeholder chunks are noted in the evidence object properties when the image is added to the case.
If you require a placeholder for a single missing segment of which you don't know the chunk size and chunk count because the image was created without the new information in the descriptive text file, this is how to find out: Change the filename extension of the penultimate segment to that of the missing segment so that there is no gap. Then rename the last segment to the now missing penultimate segment. (If the missing segment actually is the penultimate one, the last step is sufficient; if the missing one is the last, no renaming is required at all.) Then add the image (first segment) to a case in X-Ways Forensics as usually. X-Ways Forensics will bring the misnamed segment to your attention in the Messages window, which can be ignored. Check the evidence object properties for the chunk size as well as the expected chunk count and the actually referenced chunk count. Subtract the actually referenced chunk count from the expected chunk count. Now you know how many chunks are missing. Change the filename extension back to what it was before, and then create the missing dummy segment with the correct chunk size, correct chunk count, and correct extension.
With a variation, this approach also works if multiple consecutive segments are missing, just you rename more available segments to fill the gap in the first step, and you create as many dummy segments as necessary to fill the gap. Which dummy segment exactly contains how many surrogate chunks is not important as long as the total number of surrogate chunks must account exactly for the total number of missing chunks. If multiple discontiguous segments are missing, suitable dummy segments can only be created with the new information from the descriptive text file.