Can validators add metadata to their validator address?

I don’t think that’s currently possible. Some node runners asked the team to expose the node version and show it in the validator list, to see which nodes were up to date, but I don’t think the team considered adding this feature.

So far we can only edit the name, URL, fee, and enabling/disabling new delegated stake.

But to achieve what you talked about, you could create some sort of database with additional metadata (the extra information you require) submitted by the node runners from the owner’s address;

For example:
I submit a transaction from my node’s owner address to a wallet (for example the validator ranking list’s wallet) with a message that contains the required information readable and parsable by a program.
The program then verifies the owner address and matches it to a validator, and then adds the information in the validator ranking list.

This process would obviously be opt-in and would only work if lots of node runners decide to participate. We tried to do something similar with the Validator Code of Conduct but only some validators decided to join.

What kind of information would you like to obtain from node runners?