My man! I don't have much to add, your post mostly echoes what I do.
>* Clipboard history (screenshots on clipboard in the history is extra useful)
Indeed! As I mentioned elsewhere I've reversed the keyboard mappings for screenshots so that Shift+Cmd+4 copies to clipboard and Shift+Ctrl+Cmd+4 creates a file. Then I manage the images through the clipboard.
>* Snippets using the date placeholders {datetime:short} for various file naming and email workflows
>* Snippet shortcuts for things I always forget like the shortcut for → and ™ or my zoom meeting link that I paste into meeting invites
Yes, snippets are invaluable! I have tons of different ones, everything from various API keys, adding user accounts with SSH pubkey on Linux (while checking that password auth is off), outputting an ASCII guitar fretboard, setting up servers with nginx/php/mysql from scratch etc... Haven't actually looked into placeholders though, looks potentially useful although I can't think of a particular use case off the bat.
And everything synced through Dropbox of course.
>* Launching simple shell scripts by keyword
Yes! For example I often run "slack active" and "slack away".
>* Workflow for opening Jira tickets in my browser quickly
I do this as well! "<board> <ticketnumber>" opens them up directly in the browser that I use for work, i.e. "ticket 123" opens /browse/TICKET-123. Super convenient.
And for amusement I've created a couple of workflows to play different sounds, for dramatic and/or comedic effect.
And another workflow creates a new subdomain for a specific domain in Cloudflare.
Alfred is one of the main things that keep me from switching back to Linux.