Here is a revised file called "Duluth Revised" so you still have what you started with.
Comments and what I did:
You might set Location Control On. You are attempting to monitor all of the sites in Minnesota, even those way too far away to receive such as Minneapolis, East Grand Forks, Rochester, etc. This is inefficient and will lead to missed comms.
I’ve taken the liberty to add the Statewide interoperability talkgroups in the ARMER system. Lots of good stuff happens on them, such as pursuits.
You may ask the question in the Minnesota forum, but I think some of those groups you have, such as DNR, DOT and EMS have migrated to ARMER. Of course if you hear comms, then they are still on the conventional system. The interop frequencies you have are valid.
To add the Marine channels, there are two methods. One would be to add a new System called “Marine” and the a Department within that System called “Marine”. This would be consistent with how you started as you have a Railroads System.
The other way, which is what I did so as to populate frequencies is go to the full database and expand it (Minnesota>St. Louis County>Nationwide>Maritime – USA. Then highlight Maritime Operations – Marine VHF 1A-88A, right click for Append Favorites List and select the Duluth Favorites List, then click OK. Sentinel then creates a System, Department and adds the channels.
You are certainly free to delete any of the channels I’ve added (lot easier to delete than add, so I thought it best to be generous).