[MaxGabriel]

Yes. You can send Javascript to be evaluated by UIAutomation so it has all the capabilities of that UIAutomation does. There's a PR that adds this natively https://github.com/inkling/Subliminal/pull/118, but you can also just implement it yourself quite easily:

    - (void)captureScreenshotWithFilename:(NSString *)filename
    {
        [[SLTerminal sharedTerminal] evalWithFormat:@"UIATarget.localTarget().captureScreenWithName(\"%@\")",
                                                [filename slStringByEscapingForJavaScriptLiteral]];
    }