I tried many things to disable the welcome screen for Sketchup 2017 version 17.1.174 64-bit, including several registry edits like the ones mentioned in this thread and editing ATL control resources within the Sketchup binaries. Nothing helped.
In the end, I resorted to reverse engineering and editing some binary code within the executable. This worked and can be replicated in the following way:
Open c:\program files\sketchup\sketchup 2017\sketchup.exe in a hex editor
Search for the following series of hex values: FF 90 F8 02 00 00 48 8B 83
Replace them with these hex values: 90 90 90 90 90 90 48 8B 83
Save and run the edited file, and the dialog box should no longer show
