The "triangle" generally shows the most frequently + recently visited sites from your history. Do you want to hide them from the address bar but still keep your history? You can do that using a checkbox in Privacy Options.

"3-bar" menu button (or Tools menu) > Options > Privacy

Toward the bottom of that panel you should see three checkboxes under "When using the location bar, suggest"

If you uncheck History and then click the triangle, you will see bookmarked sites that you visit frequently. If you don't want to see those either, you can uncheck Bookmarks as well.

Does that do what you want?

Use these steps to remove saved (form) data from a drop-down list:

1. click the (empty) input field on the web page to open the drop-down list
2. highlight an entry in the drop-down list with the mouse or cursor Down key
   do not click the mouse or press the Enter key
3. press the Delete key (on Mac: Shift+Delete) to delete the highlighted entry

The drop-down list that opens if you click the arrow at the right end of the location/address bar shows items that you have typed or pasted in the location/address bar ordered by frecency (frequency and recency). It may not be easy to clear this list.