How do I add smart actions to f-keys on mx keys (without overwriting the media keys)?

Question

I have just purchased a new logitech keys s plus keyboard to use with my m1 macbook pro.

I want to make use of the smart keys, which lets you define custom actions on specific keys.

In the Logi Options+ software, I am able to select the key I want to define an action for. The available keys are the top row (f1 to f12 + some additional keys specific to the keyboard).

There is an option to switch between f-keys and media keys by pressing fn+esc. When media keys are chosen, the top keys represent actions like brightness up/down, play music, mute etc. When I lock it to fn-keys (or manually just hold fn button and press the key), nothing happens.

What I want to achieve is to add smart actions only when fn lock is active (or when pressing fn+key), but when I add an action to a key in Logi Options+, it overwrites the media key (mute, brightness etc), and I am not able to use the fn keys for anything.

How can I add smart actions to fn+f1 key without overwriting the f1 default action which is brightness down?