DVT SystemVerilog IDE User Guide
Rev. 20.1.26, 30 July 2020

43.49 I know that file.foo is present in the project location, but I can't see it in the Navigator View

Check if there is a Navigator filter enabled preventing the file from being displayed. Bring down the Navigator View Menu and select 'Filters':

Make sure there is no pattern in the list that matches the name of the file (like for example *.foo).