Two problem exist there:
1- electrum is not a multicoin wallet
2- I have to import 1 by 1. I don't want this.
For altcoins, I will not be able to recommend any wallet because they are close source wallets. Some of them have such function by using just a wallet app for many wallets. If you want to be able to copy the seed phrase of 10 wallets at once and paste it to create the respective 10 wallets, that will not be possible. But you can create such software yourself.
your recommendation(electrum) doesn't import multiple seed phrase AT ONCE even for BTC either. so thank you for the effort.