I am trying to implement Nested drop down for one of the drop downs we have. The options are around 250 so it would be a bad user experience for the user to look through it. Look for the picture below for a reference

When the user hovers or clicks on "Accommodation and Food Services" I want the sub-category to pop up beside it so that it is easier for the user to navigate.
Can someone please help me out with how to implement this? Thank you so much.