How to define/print different sized envelopes

A long time ago, I successfully set up different sizes of envelopes to print. I almost certainly was then using OpenOffice and an Epson printer. I’m now using a Brother printer which may or may not be relevant. I’m still able to print my previously defined #10 envelope (approximately 4.125 x 9.5 inches) though I no longer remember how I defined it and can’t figure out where to see and/or modify it’s definition.

Note in the sreenshot Preview 1.jpg, the envelope is properly shown with a size of 9.50 X 4.12 inches and that it’s oriented horizontally. Note also that the paper size is shown as Letter 8.50in x 11.00in. This is not really correct since I have the envelope in the printer. Nevertheless, the envelope prints as I would want it to.

My problem is when I try to print an envelope which I call Personal 3.6 x 6.5. Again, I no longer know how to access the actual definition of the envelope. Note in Preview 2.jpg, this envelope has a vertical orientation even though the text has a horizontal orientation.

Trying to print anyway results in a message on the printer (paraphrased) that the defined paper size doesn’t match the size in the printer. Why that doesn’t also happen witht the larger envelope, I don’t know.

I also don’t know if somehow getting the orientation of the small envelope in the preview to be the same as that of the large envelope would be at least a step toward solving this problem.

Any thoughts would be welcome.