While in “normal” mode, if the cursor is at the end of the line that is an item of a markdown unordered list, using the o key inserts a newline but does not continue with a new item in the list. In “insert” mode, with the cursor in the same location, <cr> does create a new item on the next line with the cursor ready to enter the item.
Proposed solution
Update normal mode vim bindings for o key to work like <cr> in insert mode.