Can’t add hyperlinks at bottom of text

I don’t know how this has got released, it hardly works. Anyway, regardless of that, I am trying to add text to an existing post and add an internal link to that text. The text is at the bottom of the page so the toolbar only shows the bottom part and I have to scroll right up to get the hyperlink icon. At this point it actually does nothing and the highlighted text stops being highlighted. I can’t find any way to add the hyperlink apart from typing the html code in manually. Any ideas?