When I was using Duolingo to learn Spanish, a list of vocabulary that I had learned was provided. Will the Chinese version ever provide that?
Step 1. Switch to Spanish course.
Step 2. Click "Discussion".
Step 3. Duplicate tab. (So you now have two tabs on Spanish course viewing the Discussion page.)
Step 4. Current tab: Switch to Chinese. (Can close this tab once it loads.)
Step 5. Other tab: Click "Words".
There's no need to be quick at all. It sounds like you are trying to click the "words" link in the same tab as the one you switched back to Chinese in. Steps 3 to 5 clearly say to be using two separate tabs.
Maybe Safari doesn't have tabs? If this is the case, you can instead use two separate windows or even two separate computers/tablets/phones.
Please read the steps very carefully. I haven't written "have two tabs on Spanish course viewing the Discussion page", "current tab", and "other tab" for no reason. ^^
I think it is because languages like Portuguese, Spanish and Italian have been developed further than languages like Chinese and Hindi. Just a guess. It's all volunteer ran and it takes a lot of time to do different alphabets and characters. But like I said, this is just speculation.