A userscript for Roll20 that automatically switches the character in chat when clicking on a button on their character sheet
I tested it on Google Chrome, but since it's not using anything browser specific it should work with any normal browser, like Firefox, Opera, Google Chrome or Vivaldi after installing a monkey. A monkey is a browserextension running userscripts, the three most likely relevant ones are Tampermonkey, Greasemonkey and Violent Monkey.