Can I set app specific key-bindings?

[Whyglobaleyes]

Morning All,
I think the title says it all.

• I've got a few keybindings in my ~/.config/regolith2/i3/config.d/conf file, simple things like bindsym $mod+m exec /usr/bin/thunderbird.
• I'm hoping that there's some syntax that'll allow me to set a keybinding that only works in a specific app.
• I tried an experiment with for_window [class="thunderbird"] bindsym $mod+shift+g exec /usr/bin/yad but that failed.

Is there a correct syntax to achieve what I'm trying please?
My fallback will be to bindsym to a shell script and test which app is active in that script - but besides being logically & aesthetically clumsy (at least to me) I assume that'll be relatively slow and resource hungry.

thanks in advance.