I enabled the options "transfer each file individually on background" and "Transfer on backgroud by default".
This can speed up webdav transfers significantly, by starting multiple transfers in parallel.
My problem is that parallel transfers means "starting multiple queue jobs". It does not mean "parallel transfer of multiple files in a single queue job".
Here is how you can reproduce the problem:
select multiple files (no folders) and transfer them to a webdav server -> multiple queue jobs are created -> parallel transfers are possible -> fast
Put the same files in a single folder and transfer this folder to the same webdav server -> single queue job created -> no parallel transfers possible -> slow
Would you mind adding an option "create a separate queue job for every file" to WinSCP? This would make it possible to use parallel transfers that only depend on the number of files and not on the number of queue jobs.
With this you also get a better overview, since you can see how many transfers in the queue are active and how many are waiting.
With multiple files in a single queue you only see the active transfers (and not the ones waiting).
I'm using WINSCP 5.7.7 on Win7_64bit with webdavs to a https://www.free-hidrive.com/
Let me know what you think :)