I'll find myself sorting files into folders and go through a group of unsorted files and decide, let's say, move all the cat photos to a folder labeled Cats. As I make my way down through a long list I'll be moving files to the same folder over and over in small groups. Is there a way to repeat the last move command?
A button with the command:
COPY MOVE TO=/"your alias"
or
COPY MOVE TO="your folder path"
or
COPY MOVE TO="{dlgstring|Path:}"
The last requires inserting the path every time. A way around this is saving the path and pasting it in when the request appears.
Is there a way to repeat the last move command?
I don't think there is. You could add the "Cats" folder to your favorites, either manually or by enabling SmartFavorites (Preferences / Favorites and Recent / SmartFavorites / Enable SmartFavorites™ system) and then display it in a toolbar or in the folder tree.
Another alternative is to make use of the File Collection feature:
- In the Folder Tree, select File Collections
- Right-click and select New collection
- Name it something like Organize photos and press ENTER
- Select this collection in the Folder Tree
The Organize photos will be opened in a Lister tab - Add a folder to the collection:
- Drag the Cats folder to this tab
A dialog appears: "Do you want to add selected folders to the collection as
collection members, or as sub-collections (including all contents)?" - Select Members
- Drag the Cats folder to this tab
- Repeat for other folders
Now you can SHIFT-drag your photos to the appropriate folder to move them there.
If all photos are sifted, you kan keep the collection for later use or delete it.
To delete a collection, right-click it in the folder tree and select Delete
This will delete just the collection and keeps your Cats alive 
You might find these useful for selecting files in many different places and then copying or moving them all to one place:
Since Opus can be a dual-pane file manager, you can also keep the destination folder open on the right while you go through folders on the left, selecting and copying/moving things across. The Copy Files button/hotkey will send things from source to destination in one push, without having to use drag & drop or copy and paste.