These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.04 s (backtrack: 0/20).

[ebuild  N     ] app-misc/tmux-3.7c::gentoo  USE="-debug -jemalloc (-selinux) -sixel (-systemd) -utempter -vim-syntax" 771 KiB

Total: 1 package (1 new), Size of downloads: 771 KiB