In Trados Studio 2019 I checked both ways:

• With the Community Advanced Display Filter, ensure you select Locked and press the Apply button and actually see only the locked segments. Only then, save the SDLXLIFF.
• Toolkit plugin works for me as well , I mean, I get a XLIFF with only the locked segments (I checked that with an Editor).

The problem is that I CAN’T RE-OPEN these 2 new SDLXLIFF's in Studio:

- If I try to translate anyone of them as single document, I get the error Root element is missing. It’s weird because I can see the root element in the XLIFF (I believe it’s xliff).

- If I try to add anyone of them to my project, I get the error Corrupt file: Missing sub-segment content trans-unit with ID: 43981-XXX-XXXXXXXXXX

So I can create XLIFF’s, but can’t use them, and I think it worked a few weeks ago…

PS.: I checked that these 2 plugins and Trados Studio 2019 are up-to-date.

Both methods work after installing the latest update of the Community Advanced Display Filter in Trados Studio 2019:

https://appstore.sdl.com/language/app/community-advanced-display-filter/849/