Alessandra Muzzi 

You can add sdlxliff files to a project with no problem at all. These files must match the languages of the project, that's all.

Then use the so called virtual merge. Select as many sdlxliff files in the Files view in Studio as needed and open them for review (translation). There is no other action needed.

Oops! I have spoken too early. I have created the project with all the needed files, but Studio does not allow me to open the files...

Alessandra Muzzi 

This can only happen in case the sdlxliff files are some extracts from other files. This applies to files exported during the analysis as unknown and repeated segments.

Otherwise you should be able to open ANY sdlxliff files created from ANY format. SO please check, if you are not trying to open the files for translation on the source side of the project. This is very likely, if you added the files to an existing project. You can only open files on the target side of the project.

Hi Jerzy, not sure what the issue is. I have several folders with files to review. Initially I had only imported 1 folder in the project, just for a test, and it seemed to work fine. Then I imported the other folders, but I got the issue with not being able to open the files (not even the ones in the first folder). Then I deleted the project and started from scratch, trying to import all files at once, but I got the infamous "Object reference not set to an instance of an object" error message. I have decided to stop wasting time trying to debug the software, and have resorted to an external Search & Replace tool to do my edits. Thank you anyway for having taken the time to try and help me 

Hi Jerzy, not sure what the issue is. I have several folders with files to review. Initially I had only imported 1 folder in the project, just for a test, and it seemed to work fine. Then I imported the other folders, but I got the issue with not being able to open the files (not even the ones in the first folder). Then I deleted the project and started from scratch, trying to import all files at once, but I got the infamous "Object reference not set to an instance of an object" error message. I have decided to stop wasting time trying to debug the software, and have resorted to an external Search & Replace tool to do my edits. Thank you anyway for having taken the time to try and help me 

Alessandra Muzzi 

There are no bugs related to creating projects with sdlxliff files in several subfolders. I do practice this almost every day.

I assume all would have worked fine after restarting Studio. You can add as many subfolders to a project as you wish. Never have had any problems with this, It is also possible to virtually merge (open at once) several files from different subfolders.

Using an external tool to search & replace in plain sdlxliff files bears a very high risk of destroying them. I wouldn't do that even if I have some experience with dealing with sdlxliff files in Notepad++.