You know you can use your mouse and keyboard between different Macs using Universal Control and copy/paste between them (which makes it really easy when manually migrating settings, etc., between machines), but did you know you can also copy/paste whole files using Terminal:
On the first Mac:
cat my-file.txt | pbcopy
On the second Mac:
pbpaste > my-file.txt
Piping to pbcopy is something you’ll likely find useful in general.
(You can also drag/drop files to Finder.)