Using Karabiner-Elements, you can remap cmd-alt-arrow to the Safari equivalent. I have tested, and confirmed this solves your Netflix problem.
I used brew cask install karabiner-elements
to install Karabiner Elements. You can also use the installer from their website.
You need to make a new complex modification in Karabiner-Elements with these contents:
{
"title": "Custom Safari Tab Navigation",
"rules": [
{
"description": "Use Chrome keyboard shortcuts in Safari.",
"manipulators": [
{
"type": "basic",
"from": {
"key_code": "left_arrow",
"modifiers": {
"mandatory": [ "command", "option" ]
}
},
"to": [{
"key_code": "open_bracket",
"modifiers": [ "command", "shift" ]
}],
"conditions": [
{
"type": "frontmost_application_if",
"bundle_identifiers": [
"^com\\.apple\\.Safari$"
]
}
]
},
{
"type": "basic",
"from": {
"key_code": "right_arrow",
"modifiers": {
"mandatory": [
"command",
"option"
]
}
},
"to": [{
"key_code": "close_bracket",
"modifiers": [ "command", "shift" ]
}],
"conditions": [
{
"type": "frontmost_application_if",
"bundle_identifiers": [
"^com\\.apple\\.Safari$"
]
}
]
}
]
}
]
}
Complex modifications are stored in JSON files in ~/.config/karabiner/assets/complex_modifications.
You could copy the above into your clipboard, then
pbpaste > ~/.config/karabiner/assets/complex_modifications/chromelike_change_tab.json
Or go about adding a JSON file inside of that folder with these contents yourself.
Then inside of Karabiner-Elements.app you can navigate to Complex modifications using the bar at the top, click Add Rule in the bottom-left, then enable the "Use Chrome keyboard shortcuts in Safari" rule.