The Pattern Generator supports up to 64K pattern words. Though the memory is 32-bits wide, only least significant 20 bits are used which are routed to the Arduino pins. A data word is generated once every rising edge of the sample clock.
My question is does the pattern generator support up to 1024K pattern words?
If you want something bigger you would need to modify the hardware design. I’m not sure if there are free BRAM in the design that you can use to increase the Pattern Generator memory without deleting something else from this design. You may also need to modify some of the code to support a larger size.
The hardware design and software are open source, so you can change them.
In the Vivado IPI block diagram, find the BRAM for the pattern generator, and increase it. Delete other IP if resources required.
Check the Python code for any modifications required to support larger size:
Find where this file is installed on the board and replace with your changes.