Since installing ios13.1 on my ipad a swipe from the right edge of the screen brings up a narrow browser window with whatever is the rightmost tab in Safari. I have no use for this "feature" and it disrupts an app I use in which this swipe is common

Sorry about the delay in responding. I have had my hands full at work today.

Did you try force closing Safari completely? After you force close the Safari app, I think the narrow slide over window should go away. I’m not talking about closing all of the Safari tabs I mean close Safari from the multitasking screen.

Swipe up about halfway on the home screen to get to all of the suspended apps in the app switcher. Swipe until you find the Safari preview window and then swipe it up and off the screen to close it. When you launch Safari again, that window should no longer be available in slide over.

Here's some information about Slide Over-->Open an app in Slide Over on iPad - Apple Support

Specifically: Remove the Slide Over window: Drag the top of the window off the right edge of the screen.

You have a Safari Tab in Slide Over. Swipe from the right of the screen to get to that tab. When it appears, tap and hold down on the two squares icon in the lower right corner. Then tap on Merge all windows. You may have to tap on the Safari icon again to launch the app again. Now you can close that tab if you like and the a Safari window will not longer be in Slide Over.

I think the OP’s specific issue was how to permanently get rid of the window if they accidentally swiped right to left from the edge of the screen, not just remove it from view. What you are suggesting obviously works, but if you want to get rid of it for good, the only that I have found to do it is to force close the app.