Timeline Viewer: check for overlaps when adding a file
Arranging files in the timeline viewer has been an issue since years, even in the previous version. You still have to have a deeper understanding of how a timline works if you really want to avoid mistakes with unintended overlaps etc.
Newer options like the possibility to add a file "after last file" on the timeline helps, but either it does not always catch the start and end time of exiting files correctly or users are making mistakes (e.g. not always use the "after last file" option but mix custom date-time and "after last file" in weird combinations).
However, it's still one of the biggest issues that creates frustration and keeps students from working with the tool at a very basic step (especially when they are on their own).
In the future we can try to implement the timeline in a way that is even easier to understand and/or where you can drag around your files (including overlapping / related annotations). For the current vortanz version I'm a bit afraid that new ways of moving items around etc. might cause problems or require a proper re-write of the timeline viewer.
One thing that might be easier to implement is that there is a (proper) check when you add a file to a timeline if there will be an overlap with already existing files. If yes, there will be warning before the file is actually added, that says something like this: "Warning: You are about to add the file to a position on the timeline where another file already exists. This will cause an overlap that is usually not intended unless you really want to synchronise one or more files on the timeline." With two options (buttons) how to continue: "Go back to change settings" (default) "Proceed nevertheless".