Similar to how it is done in TCG Online
Please add HGSS it's my favourite era!
This would be a huge help, and the reason I came to this website (and the lack of it is the reason I won't stay) I want to play it on PTCGO but want experience first so I know what I should be trying to build there.
Admin still needs to add the HG/SS cards onto TCG ONE though. So until that happens, there won't be any possibility of it happening any time soon.
Hayden Saul commented
This would really help if Legacy becomes competitive. Plus this format is fun to play.