If example.com is the primary domain www.example.com will automatically redirect to it. If you then wanted to add example.net and example.org(including the www) to redirect to example.com in a netlify.toml file you would need to add
E.g.
[[redirects]]
from = "https://example.net/*"
to = "https://example.com/:splat"
status = 301
force = true
[[redirects]]
from = "https://www.example.net/*"
to = "https://www.example.com/:splat"
status = 301
force = true
[[redirects]]
from = "https://example.org/*"
to = "https://example.com/:splat"
status = 301
force = true
[[redirects]]
from = "https://www.example.org/*"
to = "https://www.example.com/:splat"
status = 301
force = true