MTH responded to my question and provided a solution to the problem with the Export function in Android 10. It turns out that the app is creating a file but just no notification message when you tap the Export button. I have attached a copy of the instructions from MTH for finding the exported file.
I followed the instructions and everything worked, but here are a couple of tips that might help:
1) When I got to step 3 (top of page 3) my phone was not visible when I tapped the menu. I solved this by tapping the menu in the upper right corner and selecting the option to "Show Internal Storage"
2) At the very end, you need to select the file by tapping on the blue folder icon. Then tap the share icon near the top of the page to attach it to an email.
