Broom2101

You can search to Lemmy Explorer: https://lemmyverse.net/

Bitwarden would be a good fit for what you are looking for, especially the cross-platform aspect. Keepass-derived solutions typically require trusting multiple developers, whereas Bitwarden is developed and maintained by a single team.

From the native web app, no. You can only save the post for going back and look. Notifications only show for responses to your posts and comments.

Next: voicebot simulating concerned grandmas willing to buy gift cards…

You can download your account settings, and upload to a new account on another instance. https://github.com/CMahaff/lasim