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When you say "highlight of a text" do you mean the blue rectangles that you have in your illustration? If so, I'd have to do some experimenting. Would the rectangles all be identical in size, or would their size vary with the particular letter or character? If they're identical, you could probably make Pattern Along Path work, and use the same path as the path you put the text on (or a duplicate path). If the rectangles' size will vary according to the letter or character, I'm not sure about something more automatic than drawing each one individually. I think you might have to draw each one manually.
Do you need this to happen just once? Or are you looking to have any random string of text have the rectangles behind it? If that's the case, I think you'd almost need to make a custom font, so that each letter or character has it's own rectangle. And as far as a custom font, you might actually be able to find an existing font like that. I know I have a font, where each one letter/char is cut out of a tree shape, and another one where each letter has a star. So a font with each letter having a rectangle around it doesn't sound very unusual.