Tree view for tasks

[fkorotkov]

It will be nice to have a tree view for tasks in addition to the list view

[squidfunk]

Estimate: 8.0h

Could be combined with #172 – maybe like an analytics view for the whole run? I'd suggest doing some more research drilling down which metrics are most important and maybe re-thinking how we could represent it. If we implemented #171, implementing this is likely more a search for a small graph-drawing library, as I'd suggest to use something off-the-shelf here. I'd give it the same estimate, but doing both should be possible in less than 2 days, I guess.