I will wait a few weeks before I upgrade to 4.6.x to have it mature a bit as I do with most versions unless there's a very severe vulnerability or bug that needs immediate attention.

Submarine swaps communicated via Nostr sounds interesting and allows more decentralization of those, when anybody could become a submarine swap provider. I don't have read about the details yet, I picked it up from the release notes.

I also like the new way to add and use plugins from your Electrum wallet's datadir. I will have to take a closer look at the security measures to prevent malware from injecting malicious plugins and generally to evaluate or audit the security of third-party plugins. Closed-source plugins would be a no-go for me anyway.