how to undo actions performed by addin

Actions taken through VBA cannot be undone. Unlike in native Excel, there is no undo functionality.

Technically, you can undo the actions of a VBA procedure using the application.onundo method: https://msdn.microsoft.com/EN-US/lib.../ff194135.aspx . It looks basically like this:

1) Your main procedure must store any information needed by the undo procedure.
2) Put the application.onundo at the end of the main procedure.
3) Write and debug the undo procedure that will undo whatever you want undone.

Excel's undo stack still gets cleared when the main procedure is run, but you can undo what the main procedure did.