attribute-tableqgis
I have an Attribute-Table that I need to add a row from Excel into it.
I saved the Excel as CSV (UTF-8) and was able to copy and paste one slot at a time.
When I tried to copy and paste more than one slot nothing happens i.e.there was no error message or anything like that.
I am sure that there is a much faster way apart from copying and pasting it one at a time.
QGIS v3.x
Right click on the layer in the Table of Contents (aka. legend or layer tree) and open the Save As... dialog.
Once there, click on the Format option list and choose MS Office Open XML spreadsheet [XLSX].
Note that you also have an option for Libre Office files: Open Document spreadsheet [ODS].
ORIGINAL ANSWER (no longer valid):
Install the XY Tools plugin by Richard Duivenvoorde.
Select a vector file from the ToC (that is, make it active).
Go to Vector->XY tools->Save attribute table as Excel file.
You would need the Python library xlw installed for doing so.
To copy features from one shapefile to another you select features from shapefile a and use copy. next step is to activate edit mode in your aimed shapefile b. you can open the attribut table 
next it should look like this 
to check everything went fine, add an area row and calculate the area to make sure there is a geometry added
Best Answer
You can load the table into QGIS and as I suppose you want put this data to a shapefile, right? You can do a join based on the same ID's in the shapefile and in the csv table.