Along with calendars, the Runbox dav server hosts task lists. Calendars may be renamed through the Runbox7 interface, not the task lists.
I tried to find a way to rename a tasks list on the dav server interface … did not. Thunderbird renames the calendar only locally. My Android tasks app and the syncing app (DAVx5) do not offer that capability at all.
How to rename a tasks list?
We can look in to this for you, but I believe it may not be possible. This is because task lists are not really separate from the calendar they are stored in. They are effectively calendar items with a slightly different format on the server that let’s calendar programmes list them separately.
With the lack of tasks in the web interface it’s probably not possible to rename them. We need to look in to this in a lot more detail as the DAV server isn’t set up the way we really want it to work at the moment and there are improvements that can be made.
The other factor to consider is that some clients read/write to the calendar but may not be able to change the name so it will depend entirely on the exact tools you use with the DAV server.