Invoking an arbitrary command from a window manager

["Thomas Mueller" <mueller6725%twc.com@localhost>]

I notice many window managers, especially the smaller ones like ctwm, cwm, twm, spectrwm, and others, make it very difficult to execute an arbitrary program not explicitly in a menu.
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Some window managers usr Alt-F2 for this purpose, icewm uses Ctrl-Alt-Spacebar: very useful, I don't need KDE or GNOME.

Is there something I can put in a menu that will allow the user to input desired command line?

Not everything can be put in a menu; user will forget at least a few things, and I might want something like

uxterm -fn 8x16 -geometry 230x60 -title "nbarlene" -e login

instead of just "xterm", which leaves me scrunched in a tiny area.

Or maybe "seamonkey -P chase" when I might want to start with a profile other than default.

One computer (NetBSD 9.99.82) won't build devel/libuv, that severely limits my choice of X Window managers.

I don't know why X Window manager developers don't think of this limitation.

Tom