default or selected kernelversion does not have config value CONFIG_NFT_MASQ_IPV6.
Result is shown for kernelversion 6.7-rc3

IPv6 masquerade support for nf_tables

modulename: nft_masq_ipv6.ko

configname: CONFIG_NFT_MASQ_IPV6

Linux Kernel Configuration
└─>Networking support
└─>Networking options
└─>Network packet filtering framework (Netfilter)
└─>The IPv6 protocol
└─>IPv6: Netfilter Configuration
└─>IPv6 masquerade support for nf_tables
In linux kernel since version 3.18 (release Date: 2014-12-07)  
This is the expression that provides IPv4 masquerading support for

source code: