I updated the Tweet Marker Safari extension to version 1.2 today. This version fixes the extension to accommodate recent design changes on twitter.com. Existing Tweet Marker paid subscribers can grab the new extension here.
Here’s a screenshot of the “Set Marker” link that the extension adds to twitter.com. Then when you launch a compatible iOS or Mac Twitter app, it will scroll the timeline to that position.
If you’d like to support Tweet Marker or use the Safari extension, you can subscribe for $1/month.