Screen
The getter current_screen is here to give access to all informations about the current_screen.
How to use it
local my_field_value = current_screen.fields['my_field_slug'].value
fields
value
Return dynamic
local my_field_value = current_screen.fields['my_field_slug'].value
filled
Return bool
local is_my_field_filled = current_screen.fields['my_field_slug'].filled