How to edit a model?

I've created a model which I like to adjust now.

Here:

the docs refer to a "down arrow" - but I can't find this.
Where is it?

Additionally, I can see a small exclemation mark:
image
What does this mean? (There isn't more info / hover info)

click on the 3 dots on the upper right side of the page: edit query definition or edit metadata
image

I have a use case where the underlying table for a model was updated with a new column and an old column was dropped
In the query definition section, it shows the new column and doesn't show the old column (which is fine), but the model keeps throwing the error that it can't find the old column and I don't know how to update the model to fix this

Same problem here. Deleted column is still selected from the database "source"