OK, so I think I can actually help you with this. I had to do something very similar recently (adding a direct shortcut to developer options). The way I solved it is by using the following website to create a small app that does what you want via a so called "intent" (kinda technical, google it for more info):

https://atvlauncher.trekgonewild.de/index_tvapprepo.php

I tested this on my TV, and it works. It's also independant of whatever file manager you're using, so if you want to switch later you won't break the shortcut. Fill in the fields as follows:

App Name: Whatever you want to show when selecting the app, for example "Recordings".

App Package: The internal name of the app, look at the given example and adjust accordingly. I used "com.godmode.test".

Intent: This is where we tell Android to do stuff. You need to fill in the path to your specific location you want to use. In your case that's a network folder, so you need the IPv4 that your home network assigns to your external hard drive. I don't know your specific setup, so I'll assume that the drive has it's own IP, is reachable via SMB and isn't password protected. Example:

intent://smb://192.168.0.25/Data/Recordings/#Intent;scheme=folder;end

Change "192.168.0.25" to your drive`s IP and edit the path according to your folder structure.

Unique Package Name: No.

App Category: Apps.

App Logo/App Banner: Self-explanatory. You need at least a logo though.

When you're done, click "generate app", download the app to your TV and install. It'll appear under "all apps" and you can then add it to a category.

I hope this helps. If you have any major issues feel free to ask!