How I use FvwmIconMan
As I've set it up, FvwmIconMan is essentially a compact taskbar for my various sorts of terminal windows. In a dense display, it shows the window name for each one (well, the first part of it at least), an indicator if the terminal has been iconified, and an indicator if that terminal has the keyboard focus. This is part of how I work around not having conventional titlebars on terminal windows; the window name information from the titlebar is dumped in small text in the 'taskbar', and through long experience I can pick out the label for the current window pretty easily.
(Possibly I should make the current window more distinctive than it is right now. A lot of my FvwmIconMan configuration, much like a lot of my fvwm configuration in general, dates from days with much slower machines that had much more limited graphics.)
Left-clicking on FvwmIconMan's label for a window toggles whether or not it's iconified. Like other taskbar implementations, an iconified (or 'minimized') window is only present as a label in FvwmIconMan; to deiconify it, I have to go click on the label. This means that I care a lot about finding the window labels for specific windows, and I do two things to help with this. First, the window labels are always sorted into alphabetical order; if and when a window is renamed, the order shuffles (this is very important for my use of xterm's ziconbeep feature). Second, I give my windows very consistent names based on either the host they're on or what I'm using them for (and sometimes both). This scheme usually works okay but breaks down a bit if I have a lot of iconified windows on the same host; usually I don't and this isn't an issue. Lots of non-iconified windows on a single host are generally not a problem because they're directly visible and I usually keep them straight by how they're arranged on the desktop.
(This alphabetical sorting does mean that the label for a particular window isn't in a consistent physical spot; it can jump around wildly depending on what other windows get named or renamed. This doesn't bother me, partly because a lot of my terminal windows come and go rapidly anyways. Non-alphabetical taskbars actually drive me up the wall because I never can find anything once I have more than a few things running, or at least I can only find them by scanning through the entire taskbar.)
Some taskbar implementations only show windows from the current virtual desktop or virtual screen or the like. While I use virtual screens I have FvwmIconMan configured to include all terminal windows, regardless of where they are. Among other things this lets me easily yank terminal windows between virtual screens; I move to another screen, then iconify the window and immediately deiconify it again (windows always deiconify on the current virtual screen) with two clicks on the window's label. I can also use FvwmIconMan to switch to the virtual screen that holds a particular deiconified terminal.
(Iconified terminals aren't on any particular virtual screen; they've been effectively swallowed by FvwmIconMan.)
Sidebar: terminal windows versus Firefox windows
A long time ago I would have confidently told you that I did this for terminal windows, and only for terminal windows, because they were by far my most numerous sort of window and I also often had a lot of them iconified. If I had the iconified windows represented as real icons on the root window, I would run out of space; therefor I condensed them all into a much more compact area. Then my Firefox window habit grew out of control and at this point I often have as many iconified Firefox windows as I have terminal windows.
So why do I have a taskbar for terminals and real icons for Firefox?
The simple answer is that useful Firefox window names are too long,
whereas I can make
xterm window names short enough that I can pack
them in very compactly. Because Firefox window names are long, a taskbar
that showed enough of the titles to remind me what they were would be
too big to be feasible. Instead it actually takes less space to have
real icons and count on my spatial memory to
remember what the Firefox icon over there is for.
(Well, the spatial memory plus the bit of the start of the window title that fvwm shows me below the actual Firefox icon.)