When Krusader users utilize the "Host" comboBox on the "New Network
Connection" dialog: they often see bad suggestions because there are obsolete
entries, mistakes and so on, but normal Krusader users can't remove those
entries. For example, web browsers have Shift+Del in order to remove the
thwarting entries.

With a KrHistoryComboBox, Krusader users are able to delete wrong entries
from history lists, and therefore they can remove those bad suggestions that
they were seeing.

Press Ctrl+N to open the "New Network Connection" dialog. Using the "Host"
comboBox on the "New Network Connection" dialog, several times: add a new host
address (e.g. a non-existent one like "example.com"), press the «Connect»
button. Open the "New Network Connection" dialog again, delete the recently
added host address:
a) using Shift+Del when the popup list is seen;
b) or using the arrow keys and Shift+Del when the popup list is not visible;

Try to delete all the host addresses until the list is empty, press Shift+Del
again. Press the «Connect» button.

Open the "New Network Connection" dialog again, check that the list is empty.

Start a new connection (e.g. an FTP one), just in case.

Note: Those changes are designed to be tried after applying the ones
described in https://phabricator.kde.org/D28961