When you switch pages, you lose all tapped translations you tapped on which makes it jarring to back up in readings.
Also I wish the amount of words per page was consistent and didn’t shift around as you tap on words to see translations. Makes it akward to read and things keep shifting around
Sorry. This is just how it works for the time being. I have been considering adding a different translation display mode which doesn’t adjust the layout of the underlying text. (No promises though.)
About retaining the highlights upon switching pages, there is this feature which is related but not exactly what you are talking about: Auto Highlight Words As You Read - Readlang Blog