You can set the latency manually but first you must got to "Settings" (gear icon) then "General" then toggle "Show advanced options" to on. This will expose a bunch of new configuration options, both in the settings and in a few other places in the app.
Once you have enabled advanced options you'll see a "link" at the bottom of the Latency Calibration screen that says "Manual configuration...". That will let you manually configure the input and output latency.
It's unfortunate that this wasn't easy for you to find but I'm glad you said something. I wasn't sure whether anyone would know what to do with this, so you've at least validated that it's worthwhile to have that option.