Potlatch once could do this:
Ctrl+Alt+1 – Ctrl+Alt+9 add preset tags to memory 1-9 Example: set bridge=yes and layer=1 on a way and press Ctrl+Alt+1 to save it to memory 1 (via cookie) ⇧ Shift+1 – ⇧ Shift+9 use preset tags previously saved to memory 1-9 Example: ⇧ Shift+1 to set tags from memory 1 on a selected way or node
Seems to be gone or changed in Potlatch 3.
Basic need is to be able to copy all tags from an item and paste them onto another one. Typically select all from a node and copy them to a way. Afterwards empty or delete the node.