Selecting a marker in either the timeline or on the map will update the URL with a fragment id. The new URL, when shared, will highlight the correct marker. Note, it will then be impossible to share the whole timeline without a selection, short of editing the URL by hand.
These URLs will only do the right thing if the source data doesn't change. This is due to a limitation of Timeline JS. The fragment ids correspond to the index of the record, once the records have been chronologically sorted.
I would love to be able to share URLs to individual items in a timeline instead being only able to link to a whole timeline.