The custom trigger option gives you the ability to design your own custom trigger that fires up the accessibility toolbar. This helps to adjust the trigger location, look & feel based on your website design.
Don’t add a custom trigger in the footer.
Please add the link in the header and not in the footer.
Think of a keyboard-only user who doesn’t use the mouse. Such users have to keep pressing the TAB key at least 50 times to open the accessibility toolbar.
Plus, if he is a first-time visitor he will not have any clue about the presence of toolbar at all.
Hence add it in the header part. So that’s the first thing he/she will open when they visit your site.
To know how to build your own custom trigger, Click Here