Link releases are handled via a GitHub Action; see .github/workflows/make-link-release.yml for the details. It will create a new release upon detecting a new tag beginning with the letter "v". For example, if you want to create a new release v4.0.18, do the following:
git tag v4.0.18
git push origin v4.0.18
and the release should get baked. A release will contain two assets, one for Dyalog version 18.2, and one for version 19 and later.
Note that the action does NOT validate the release sequence in any way. It is up to the person making the release to compose the tag appropriately.