Any command requires you to hit enter to start it.
2020 and prior - TRim, enter, pick to start a crossing window
2021 - TRim, enter, pick to start a crossing fence
In my mind the fence is the same as crossing.
But, you want TR for a quick key, but you still have to hit enter after typing TR,
TR, enter, start picking.
By setting the Quick mode in the code I posted you will get the crossing window, or at least I do here in my testing.