Hello there, Hedelstein. Currently, there's no option to set a custom date range for viewing transactions using the QBSE mobile app or mobile browsers.
You're correct that the available presets are for the past 3, 6, and 12 months. Other options include this month, last month, last year, and year-to-date.
To view transactions outside these ranges or for a custom date range, I recommend logging in through a web browser. There, you can filter transactions by any desired date range.
Here is a sample screenshot showing how to set a custom date range using your web browser:

This thread will remain open for additional questions. We're always here to help.