Once the screenshot is taken, you'd need to use a photo editing tool like Photoshop to edit it. Before you take the screenshot, it's pretty easy to edit things like websites where you can just right click, select inspect, and change text to whatever you want. More on reddit.com

Many posts on this...

Fix this, multiple users have this bug

Can't quote

Reddit edit tool line is broken since last change 2 days ago. Objects overwrite each other making Cancel button impossible, etc., etc.

there's this bug where this happens

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command-control-shift-4 then draw rectangle around what to capture command-space to bring up spotlight, then type in pre and hit enter to launch Preview command-n to create a new file from was just captured to the clipboard command-control-r will bring up the annotation bar and place a rectangle using the last-used styles, or command-control-t will add a text box once done annotating, click once in an empty area to make sure no annotations are selected command-a to select all command-c to copy the entire thing - including annotations - to the clipboard Once pasted, go back to Preview and hit command-w to close, click Delete so no file is saved. I use this process to paste marked up web pages into Jira all the time without creating a single file. More on reddit.com

The only thing you can do is erase the existing text with the eraser tool in an image editor. More on reddit.com