Hi,
With the release of Syside v0.8.0, we have deprecated the old “SysIDE Editor Legacy” extension (extension ID sensmetry.sysml-2ls) and replaced it with a new “Syside Editor” extension (extension ID sensmetry.syside-editor). The new extension is still free-to-use.
We strongly recommend switching to the new extension (VSCode Marketplace, Open-VSX), which has many issues fixed, while also being significantly more performant.
For more information about the switch, read our announcement.