The latest version of a community created Step does not show up in the Workflow Editor. The new version is available in the Step's repository but it can't be selected in the Workflow Editor.
Creating a new GitHub release in the Step's repository is only part of the whole release process.
The Step creator has to notify Bitrise that there is a new Step version available. To do so, the Step's creator has to open a new PR to the Step within the Bitrise Step Library.
In general, the above process might take some time, but if you think the Step creator has not opened a PR to Bitrise, you can also ask the Step creator if the pull request has already been made. If all goes well, you'll have the new version available soon in your Workflow Editor!