Easier/faster editing: Working with 2 or more timelines.
First you take the best parts of your footage with setting in/out points and insert it into a timeline. So you can make even more then 1 in/out point in a very long clip. Now you have all your best clips selection on a let’s call b-roll selects timeline.
Now you open/create a new 2nd timeline for the final video (master/project timeline). Stack it below the b-roll selects timeline. Now you can drag and drop all needed clips from the b-roll selects timeline into the master timeline.
To do this no nested timeline is needed. You should have the possibility to assign the b-roll selects timeline to the clip monitor so you see on the clip monitor your selects and on the project monitor the final video.
Some link for better illustration:
https://www.youtube.com/watch?v=s71kPGsCjGA -> with some link to the history of have more than 1 timeline.
Maybe it’s part of: https://phabricator.kde.org/T1959