By default, the custom indexes are set to unset. With this status, they use the default web indexes provided by nRF Util.
After adding a custom index, you can permanently specify a different index for use with sdk-manager by using the config sdk-index set or the config toolchain-index set subcommands (for SDK and toolchain, respectively).
For example, the following command changes the sdk-index to use the lcs2 index:
nrfutil sdk-manager config sdk-index set lcs2
lcs2 index. (You can still use the --sdk-index flag for single commands to override this setting.)
To unset a custom index, use the config sdk-index unset or the config toolchain-index unset subcommands (for SDK and toolchain, respectively).
For example, the following command changes the sdk-index back to the default unset value:
nrfutil sdk-manager config sdk-index unset
Tip
You can also unset a custom index by removing the related custom index.