How to fold a letter with address showing

Different type of answer.

enter an address in a letter so that it shows in an envelope window?

Open a new Write document, do Insert > Envelope > Insert, clear anything in the addressee frame out of it and put your cursor in the home position in the frame. Do Crtl+F2 > Variable tab and select User Field, name it, make sure Format is set to Text and click Insert.

Leave the dialog up but scroll down to the letter and place your cursor at the position where you want to type the address. In the dialog select Input Field, click Insert, tap the spacebar twice and click OK. Close the dialog.

When you hover your cursor over the field in the letter it will change to a finger, click, fill in the address and click OK. Note that the address appears both places.

Now, if you save this type of file as a template, you will be prompted for the address when you create a new file from the template.