I needed something to explore aspects of my ancestor tree and while Greg's Ancestor Webs almost gave it to me, it's not quite there yet, so I decided to roll my own. While it was intended just for my personal use, it turned out possibly being of use to others as well, so I'm telling you all about it in case you have a use for it. Here it is (before using this link, see the 2nd update below): https://apps.wikitree.com/apps/smit641/ale/
The "ale" stands for Ancestor Line Explorer. The idea is that you can load X generations of ancestors from WikiTree and optionally specify some people of special interest. When the tree is drawn, the (blood-)lines to those people will be highlighted. You can control (to some degree) how the tree and lines should be drawn (only the lines of interest, the whole tree, or only up to a certain level, etc.).
Please read the help text (click on the ? in the green circle at the top right of the start page). Have fun and let me know if you find any issues. (Some "issues" might be features .)
[Edit: this app was not really intended for a small screen, but there has been reports that it is usable there as well.]
Update: In the past, people occurring more than once in the tree were marked with coloured squares and if you clicked on a square, all other occurrences of that person were highlighted (clicking a second time turned the highlight off). In the current version, that still happens, but in addition, the lines from the root to each occurrence are also highlighted.
Another Update: I have incorporated this tree view into the Tree Apps and it is in the queue to be approved and officially released. In the mean time you can test-drive it at: https://apps.wikitree.com/apps/smit641/dynamic-tree/#view=ale
Final(?) Update: This app can now be found on any WikiTree profile as Ancestor Line Explorer on the drop-down under Tree Apps.