Development suggestion for the register

Are you talking about the Quicken Mobile app?

In Quicken for Windows you can change the register's sort order. If you change to "Order entered", the most recently entered transaction stays at the bottom of the register. The next new transaction you enter will stay right below it, and so on.
This Sort Option is available from the register's Actions gear icon, Sorting options, by Order entered.
To change back to your regular sorting option, by Date, select it from the Sorting options popup or simply click the Date column header in the register.

I don't use Q Mobile myself, so I don't know if a similar function is available in the Mobile app. Can you check?

I'll see if I can get a moderator to fix the category to Windows, Investments.

To clarify, we're discussing an issue with Quicken for Windows and working in investment account registers.

To the best of my knowledge, unlike in banking account registers, there's no sorting in investment account registers other than by Date, by Security, by Clr, or by Action.

To enter a number of transactions, one right after the other, have you tried the Enter Transaction dialog? It allows you to fill out the form for one transaction, press the Enter/New button to save the transaction and start a new one right away.

As to QIF files ...
dates using US format mm/dd/yyyy with a 4-digit year should work fine, 19yy, 20yy or any other century.
Ditto for dates with mm/dd'yy (with a quote) to indicate a 20yy year

Dates with mm/dd/yy are supposed to follow your Windows Date format settings for the sliding 100 year rule, if programmed correctly. No guarantees.

In the example above, a 2-digit year between 60 and 99 is converted to 1960-1999, and 00 - 59 is converted to 2000 - 2059.
If you must work with 2-digit years for 19yy dates, try this option set to 1900 and 1999.