How can I copy and paste dimensions to make objects the same size? How can I copy dimensions of the first object and paste them onto the second bigger cushion so that they become identical, whithout having to copy and paste single dimensions on the n-bar?
If you enable Align Tools Add-on in the Preferences(F4-&gt;P, or Edit -&gt; Preferences):

You will have Advanced button in the sidebar, Item tab:

You can then select the objects you want to scale, then select the one you wish to scale to so it's the last selected and active and hit Advanced under Advanced Align Operations:

In the Last Operation panel you will have Fit Dimensions: