After shifting some of the columns to the left, I have lost some of the
column labels;
my worksheet begins with column A, then C,D....,M,R,S, etc. I.e., I've lost
column labels B, N, O, and so on. Is there an easy way to restore all of the
column labels in their correct alphabetical sequence?

Thank you for any help you can provide

Most likely you've inadvertenly hidden columns, rather than lost them.
When you look at the visible columns, say A and C, is the vertical line
between A and C heavier than the separator between C and D?

Try this: highlight columns A through C by left-clicking on A and
dragging over to C. Then right-click the selection and select UnHide
from the menu. B should then appear.

Thank you, Dave!

That did the trick.

"Dave O" wrote:

Most likely you've inadvertenly hidden columns, rather than lost them.
When you look at the visible columns, say A and C, is the vertical line
between A and C heavier than the separator between C and D?

Try this: highlight columns A through C by left-clicking on A and
dragging over to C. Then right-click the selection and select UnHide
from the menu. B should then appear.

Glad to help!