The file contains these options:

acme

The ACME account to use on this node.

acmedomain0

ACME domain.

acmedomain1

ACME domain.

acmedomain2

ACME domain.

acmedomain3

ACME domain.

acmedomain4

ACME domain.

http-proxy

Set proxy for apt and subscription checks.

email-from

Fallback email from which notifications will be sent.

ciphers-tls-1.3

List of TLS ciphers for TLS 1.3 that will be used by the proxy. Colon-separated and in descending priority (https://docs.openssl.org/master/man1/openssl-ciphers/). (Proxy has to be restarted for changes to take effect.)

ciphers-tls-1.2

List of TLS ciphers for TLS <= 1.2 that will be used by the proxy. Colon-separated and in descending priority (https://docs.openssl.org/master/man1/openssl-ciphers/). (Proxy has to be restarted for changes to take effect.)

default-lang

Default language used in the GUI.

description

Node description.

task-log-max-days

Maximum days to keep task logs.

For example:

acme: local
acmedomain0: first.domain.com
acmedomain1: second.domain.com
acmedomain2: third.domain.com
acmedomain3: fourth.domain.com
acmedomain4: fifth.domain.com
http-proxy: internal.proxy.com
email-from: proxmox@mail.com
ciphers-tls-1.3: TLS_AES_128_GCM_SHA256:TLS_AES_128_CCM_8_SHA256:TLS_CHACHA20_POLY1305_SHA256
ciphers-tls-1.2: RSA_WITH_AES_128_CCM:DHE_RSA_WITH_AES_128_CCM
default-lang: en
description: Primary PBS instance
task-log-max-days: 30

You can use the proxmox-backup-manager node command to manipulate this file.