Currently when plugin support is disabled, attempting to add an "Execute an External Plugin Function" action pops up the "No plugins available" messagebox, saying "There are currently no plugins available to select for this action.";
While that is technically correct(the best kind of correct), I feel it may be useful to add a warning to this message when plugin support is disabled to alert the user to this fact, possibly even instructing the user how to enable it.
A reference to the "Disable plugin support" checkbox of the CTRL-SHIFT load options menu could be added as well, just in case someone was instructed to check a number of the load options but is now wondering why their plugins don't work, but there's already a "Plugin support force disabled" message in the log(and I doubt the majority of plugin users, which I assume are HCS users, actually modify the "Execute an External Plugin Function" action itself).
EDIT: Messages are shown, checked in v1.7.8