How do I keep one column on the display all the time while working in other columns?

If it is the leftmost column, convert it to a header column (if not one already) and "freeze header columns". Right click on the column letter to do both those things. Header columns are special in Numbers, they are meant to be used for headers, not data. You can have up to five of them and all five will be frozen (or not).

If that column is on the left then you can define it as a Header Column. One way to do that is go in the menu to Table > Header Columns and choose 1. Then you can freeze it by going to Table > Freeze Header Columns.

You can have up to 5 Header Columns.

More here:

Add or remove rows and columns in Numbers on Mac - Apple Support

(You can also access the User Guide via Help > Numbers Help in your menu.)

SG