When I started to work on the RE4B book in 2013-2014, I used the Ditto clipboard manager heavily, that proved itself incredibly useful when working with large-scale texts. I still use it when I forced to use Windows.
Also, I use VIM registers heavily, and Emacs kill-ring. (Depending on the phase of moon, I use both editors.)
After I switched to Linux completely, I tried to find a good clipboard manager. And as a strong adherent of the suckless philosophy, I use dwm and st terminal and dmenu, of course. So I picked clipmenu, but I've found it too complicated. I wanted something even simpler.
Also, two X Windows clipboards is just yet another horrible story. This still irritates me a lot. You can never be sure what clip is in which clipboard.
And so I came up with my own homebrew solution. Usually I have two tmux windows, the first I work in it, the second has the windows I need rarely: dropbox status, thinkpad battery charge status, even IRC client, etc.
I wrote two scripts: the first shows current status of both clipboards (shell), the second dumps history of clips (Python). Screenshot (this is terminus font, of course). Tmux script to run it all at the startup. When I need to see a clipboard history, I switch to another workspace, yes.
When you want to reinsert a clip into a (primary) clipboard, just select it using mouse. When you want to search within clips, use tmux: Ctrl-B [ /, then, again, select it using mouse.
As simple as that. Now I'm happy. All the files are here. I think, you can run this in GNOME or KDE...
Please drop me email about bug(s) and/or suggestion(s): firstname.lastname@example.org