dark/light switch in thunderbird email

linux 21.2, runbox.com, thunderbird 115.5, on a website, https://urbansurvival.com/quadwitcher-for-insane-market/, i visit, i am allowed to use this switch, sorry i also use vivaldi as my browser, and i copied what i am trying to show you, but it refuses to paste. At least you have the website, which will have the switch in the bottom right hand corner. Anyway, it is a little switch in the bottom right hand corner of the website that allows you to switch the colors from light themed to dark themed. The dark theme has a shade of white writing on it. Thunderbird has dark fox as an add on, will that do the same thing? will it come in the form of a switch? so i can go back and forth from light to dark to light, depending on my mood???? Thank you...b3 for the record, i also have no idea where the clipboard is in vivaldi/thunderbird. I can see it is on the clipboard, but no idea where the clipboard is. For even more record, i would like to have 6-10 items on the clipboard and be able to take them off the clipboard and put into my emails depending on the recipient.