You may not know it, but it is possible to select multiple words or groups on a web page displayed in the Firefox Internet browser, in the same way that you would in Windows Explorer.
After having selected the first word or group of words, hold down the keyboard’s CTRL key and select everything else that you want on the Web page. The selections will become highlighted one after the other.
This will allow you to highlight aspects that you want for presentations, as well as copy and paste the contents that you desire. It should be noted that in this second case, you will have to copy the text in the right order, as the pasting is done in the order that the text was selected.