I am using Xubuntu 18.04.
This question specifically pertains to Xubuntu (in my case: 18.04):
I frequently see myself first pressing
Ctl+L in order to let the open file or the save as dialogue let me enter a full name.
In fact, I often have some Thunar open and there I first do
Ctl+C to copy (the full path) to the scratchpad in order to paste it from there to some file open dialogue or to some save as dialogue (in the latter case to modify the file name part before actually storing).
This approach guarantees that I use similar file names for similar things (e.g. just change a date part in them or other parts differing from an existing sample).
It would fit best to my habits if the box letting me enter a full path or just a filename, if that relates to the shown directory, would be shown rightaway instead of the so-called breadcrumb navigation.