Please note that you will need to install the Editor from the VS 2015 supported version (direct link).
Once it is installed, the default app for opening .XLF files needs to be changed within Visual Studio. To do this, right click the .XLF file and select "open with…" When the UI is displayed, select the Multilingual Editor and click the “Set as Default” button. This will enable opening of the XLF file in the Multilingual Editor by default.
.Net Core and net standard projects
This build support enabling and localizing .Net Core and netstandard projects. However, the .XLF file's build action is not automatically set to XliffResource. This will need to be set manually after adding a new target language to ensure the translations are placed in the related .RESX file(s) during the build.
This is required as Visual Studio 2017 enables side by side installs (Enterprise, Community, etc.). To ensure SxS works, all VS Extensions need to be installed via the VSIX model. The VSIX model does not support installing stand-alone apps so a separate installation step is required.
For more details on Visual Studio 2017 SDK changes, please see the "What's new" Visual Studio extension documentation.