You can launch the game directly from the Launcher and bypass the Ignite screen; Ignite's usefulness is more for the Free Loot box and the elusive chance of getting the rare goods in there.
As for how to get Ignite to recognize Scarlet Blade is installed...I'm trying to get that working myself on a secondary PC. I had to reinstall Ignite and it lost the game links.
Alternative to Ignite Play:
Default install: C:\AeriaGames\Scarlet Blade\
Right click and Send to - Desktop Shortcut on SBLauncher.exe