I'm not sure what you mean by by the vector code being modified on demand. So I might not have the whole picture (so to speak). It sounds like you're making a webpage?
Maybe you could use a text character, such with UniCode, rather than drawing a circle? Then you would "type" it at the end of each text. And it would always be at the end of the text, no matter where the text ends. In Windows, you could use the Character Map, which you can find....well, I don't have Windows 10, but it's probably still in Accessories. Or you could use a font which already has such a character.
If you have to use a circle rather than customized text....or even if you do use a special character, you might try right justifying the text. Then as you type, the text "expands" towards the left. It would never go over something on the right, like the circle. That button is on the Text tool control bar (and I think also in the Text and Font dialog) and looks like this
Although using right justified, the text could expand over the image to the left. So using a text character for the circle might be the best solution. I mean, you can't have an immovable object on both the right and left, and still have space for any amount of text in between.