Symfonium 7.0 allows you to configure the notification and media session buttons.
Please note that those buttons are now linked and that the positioning of the skip next and skip previous are mostly enforced by Google.
If you disable skip next and skip previous you have access to up to 5 options. (Depending on your OS version and where you are looking)
Settings
They are available from Settings/Playback/Configure notification, media session and headset buttons.
Media session (Android 13+)
In the notification shade this only support 4 actions with the skip previous and skip next position being fixed.
So if you enable both of the skip option, the action button 1 will be in position 3. If you enable none, then action 1 button will be at position 1.
Note: Some OEM like Samsung may display this differently and you need to test to adapt.
Notification
This only support 4 actions with the skip previous and skip next position being fixed.
So if you enable both of the skip option, the action button 2 will be in position 4. If you enable none, then action 2 button will be at position 2.
Android Auto
This support 5 actions with the skip previous and skip next position being fixed.
So if you enable both of the skip option, the action button 2 will be in position 4. If you enable none, then action 2 button will be at position 2.
Please note that if you do not enable the 5th action (or the 3rd if you enable both skips) then the 3 dots menu is not visible and all 4 actions are directly accessible.