There is a plugin that does exactly what you want - and it will do it in one click.

Plugin Name:  Chord Line - Keep Bottom Note

Click here to go to the Finale plugin repository:  https://www.finalelua.com/scripts 

Install the plugin, restart Finale, highlight the region requiring the action, then run the plugin.

If you are new to Finale Lua Plugins... go here for install instructions: https://www.finalelua.com/help/install 

There is also a plugin that will keep only the top note in chords - also in the repository.

If you press CTRL+Arrow Up/Down after selecting a chord, that should cycle through notes in a chord individually to edit/delete them.

You did not mention but if you have 27.3 you already have a few updated JW plugins. You want the one called JW polyphony.

No need to search for it or install it as it is included you don't have 27.3 you need to upgrade.

I'm sorry. I have version 26.3, but I think I figured it out. Thank you

There are a number of ways to do this in both Simple Entry and Speedy Entry. All are found in the manual.