At this time, there isn't a QuickBooks Data patch for QB Mac 2019 to integrate with QuickBooks Windows 2019. This is because the QuickBooks Mac has a different interface and operating system with the Windows.
The available option is converting your Mac data file to Windows. If you'd like to try this, I recommend checking the link below. It provides the restrictions and detailed conversion process.
Re: Has QB Data Center issued the patch for QB Mac 2019 to integrate with QB Windows 2019?
I think bcmillet is referring to the bug in QuickBooks Windows where it won't import a Mac exported .qbb file. My understanding is that this fix is going to be in the R6 version of QuickBooks Windows 2019 (and also in updates to earlier releases of QuickBooks Windows). I don't know if R6 has gone out. I'm also not on the QuickBooks Windows team so I don't know for certain that the fix made the release. But that was the plan.