A Visual Studio extension (VSIX) which creates codelenses allowed to goto to sync sibling method for async methods and vice-versa even if sibling method is in different file or code generated (for example, via source generator).
When you types the codelenses are in watinig state. After few second after you stopped typing, the codelenses are recalculated. This timeout can be found in Sync <-> Async options tab in VS options window.
You can download this extension from VS marketplace.