via multiple transactions and multiple addresses. But of course I then realized all these multi transactions to the second hidden wallet could possibly be linked via the common sending address.
To analyze if your transaction behavior could indicate to malicious parties that all funds which came originally from the original wallet's address are still yours, there are two questions to answer:
1) were the transactions to these wallets made close together, e.g. in the same hour?
In this case, everybody analyzing these transactions (scammers, chain analysis companies) would probably assume all the other addresses are also yours. You could thus mark all these addresses as "compromised". It is better to do this whole transfer process over the course of several days or even better weeks, with amounts which aren't similar to each other, so they look like ordinary payments.
If you did this, or if the single transaction to your hidden wallet was the only thing you did, my advice would be to start again with the process. In all periods with low fees, transfer some BTC (not the entire balance of an address) to another address, trying to vary the amounts, the timeframes between transactions, etc. so they look like you're making ordinary payments.
Take into account that in this process you should never re-use any address, because they could linked together again if you make a mistake (e.g. mixing two different "branches" of your funds).
2) does the software of the hardware wallet group all wallet addresses together when they request data from a blockchain node to know the current balance?
This is a common problem of software wallets like Electrum or Sparrow, and as a hardware wallet isn't a full node, it could suffer from the same problem - it could depend on the provider. It's suspected that for example in the Electrum network there are also chain analysis firms operating servers which try to link different addresses together if they detect a request of several addresses at once from the same IP address, which is was Electrum normally does.
If this is the case, and you want to go 100% safe for privacy, you would have to create a hidden wallet for every part of your balance you want to separate.