@dangillmor https://mastodeck.com/ does a great job of looking like TweetDeck columned layout.
https://elk.zone/ does a great job of looking like the native Twitter web interface.
Here's the native setting from the social instance:
https://mastodon.social/settings/preferences/appearance
@dangillmor If you want to add the local feed of other instances than yours: I don't think that's possible.
That being said, to pin a new column in the advanced view (which you seem to already have selected), you can do the following (I can't do screenshots on my current device, sorry):
@dangillmor What state are you in now (another newbie using the advanced interface)?
I have been able to add columns with Home, Local Timeline and Notifications, and a 5th that usually shows Federated Timeline.
You want columns just showing posts from those hosts?
So here I have done a search for #uknews, then I click on the result and it opens in a column, then you select "pin" from the menu, top right...
Please, please, somebody.