In the case of a task, the tree list provides:
Note that a group member has a zero delay implicit link with its group (it will be a link with group beginning), however you can create an explicit link with its group to define a delay which will have effect only if it is more than zero.
In the case of a group,the tree list provides same information except those are not existing for a group : duration, member of group indication (a group cannot be a member), fixed end indication (no fixed end for groups), realization ratio and workload. More you have a list of members.
In the case of an event, the tree list provides same information except those are not existing for an event: duration, end time, realization ratio and workload.
When you select a line that can be modified or deleted (it starts with a small circle), the action bar commands allow doing authorized changes, deleting line if authorized, or creating new links.
When there is no selected line, the options menu allows then: