I have a left hand sub navigation, what I want to do is have it so when the dropdown is opened and you visit pages within that dropdown, the dropdown will still be expanded to show what page you are on.
However, I cannot say for certain. Most likely you will have to add some custom CSS to make sure the dropdown stays open after a link is clicked on it. Unfortunately, that is beyond my knowledge.
Roll your own dropdown with IX2. Webflow’s dropdown element is designed and coded to do what it does. When you want custom behavior you need to build that out yourself.