For every person it can be different there were 3 different versions on the older page ExternalViewers - Working Advanced Settings Strings
and none of those are the current version 2018 nor any of the special variants
As KJK has pointed out it is best to test outside SumatraPDF (use a simple cmd prompt) the try and understand how it differs inside the settings file where a %p replaces a page number and “%1” may not require the quotes
So place a pdf in an easy to find location such as c:\test.pdf then check what needs to change in a command line so that using my win10 64 bit version
“C:\Program Files\Bluebeam Software\Bluebeam Vu\2017\vu\Vu.exe” c:\test.pdf
will open that file once it does then next test is rename file to c:\name with space.pdf
now check that you can open the same file without error messages from the system about the file name breaks. then add the command into SumatraPDF settings with %1 for the filename test the file with spaces in the name works
If you get feedback along the lines of Error cant open file “name.pdf” cant open file “with.pdf” cant open file “space.pdf” then the file name needs “quoting” so change it to “%1”
Looks like Bluebeam Vu on win 10 accepts filenames with spaces so the following should be final working version of vu (2018+ will only be Revu)
“C:\Program Files\Bluebeam Software\Bluebeam Vu\2017\Vu\Vu.exe” %1