I want to delete a constraint on a view in Android Studio?

You can delete a constraint by doing any of the following:

• Click on a constraint to select it, and then press Delete.
• Press and hold Control (Command on macOS), and then click on a constraint anchor. Note that the constraint turns red to indicate that you can click to delete it
• In the Layout section of the Attributes window, click on a constraint anchor.

Source

Add or remove a constraint

Just delete it in "Code" view, I think it's way easier to do things like this there. (Normally in the top-right corner you have three buttons when you have a layout file open: "Code", "Split", and "Design".)