If the part of code that you want to target with your suggestion is something else than one full line, it's good to notice that there are different views of the code with subtle differences. The difference comes from what you have selected in the Files tab file explorer (the tree with folders and files):

• If you have the full tree selected (which is the default), or some folder selected: you only have the comment bubble available next to the line number, and by clicking that, you can only target one full line of text.

• If you have a single file selected in the tree, the view is slightly different (although looks almost the same). In this mode you are able to mark some area of the text with your pointer and target that area with your comment and suggestion. In this mode you get the comment bubble shown in answer from @Tore Aurstad. You can select a part of line, or you can select multiple lines. This can be really useful, especially if you want to make a suggestion that changes multiple lines.