actually if i select the 'manually-edited' manifest in the facet configuration, i can either select the default path to manifest - and in this case the file will be created if necessary - or select the non-default location. In the last case i can choose the existing manifest via browser.
However, i cannot point to teh directory that doesn't contain manifest.mf yet or create new directory in this dialog.
Generally, i can type the path (even the not-existent folder) right in the filed manually, but this is not evident and convenient way.

It would be nice to have possibility to point to any directory in browser (to use the existing manifest or create new one) and to create new folders in the same dialog.