Copy-paste History

Implicit

RegisterContent
"Effectively last used register. Writes to register 0.
0Last yank.
1d/c with %,(, ), `, /, ?, n, N, { and } or whole line.
-Last small delete (less than a line). Can be the same as 1.
2-9Last content of 1, 2, etc. 9 is lost.
+ *System clipboards (X11/Wayland clipboard and primary).

Explicit

RegisterContent
a-zNamed, use freely. Doesn’t fill numbered registers.
A-ZAppend to that named register.

Read-Only

RegisterContent
.Last inserted text (similar to . to repeat).
%Current file name.
#Alternate file name.
:Last executed command line. Run with @:.

No Read or Write

RegisterContent
=Run an expression.
_Black hole.