Hi GNUser
 ... but the application that was complaining about that missing library continues to complain. Adding the library to onboot.lst and rebooting makes the problem go away. (This comes up when checking for a new extension's dependencies; having to reboot after adding each missing library gets tiresome.) ... 
Something is off here. An extension won't load if something listed in its  .dep  file can't be found. Upon rereading you your original
post, it sounds like you might be creating an extension and the  .dep  file does not exist yet. By the way, dependencies should not
be listed in  onboot.lst.  To find the missing libraries an executable requires, do this:
ldd Path/To/Executable | grep -i foundThen using the  Apps  utility, click on the  Search  button and change it to  Provides.  Type the name of the missing library in the field
to the right of the  provides  button and hit enter. If the library is available the extension(s) providing it will show up. You can then
change the  OnBoot  button to  Download + Load  and load the extension without it being added to  onboot.lst.