While editing Task, user may choose Workspace. Selection list is cleverly done with filter edit field, so use can enter few chars initiating workspaces list to be filtered to just those containing typed text.
But, for Milestones and Tags, this is not the case. Plain drop down list is used, which is not efficient, especially there are potentially more milestones and tags than workspaces so it is more important to have usable solution for finding them in lists.
