For new attributes (layers, pens surfaces, etc.) you can use the Attribute manager to transfer from one file to another.
Things like new section/elevation lines or views, you will need to create them manually.
Layouts you can copy from one file to another but any drawings on them will remain linked to the original file - so you will have to re-link them to the new file.
it is easier just to create new layout pages.
Anything that you have modelled, you can just copy and paste.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11