Most of the bidules have a toolbar in their user interface.
The first one is to bring up the parameter properties dialog, the second
one the parameter locking dialog, the third one is to randomize the parameter
values and the fourth one is to "mutate" (i.e. slightly modify) the parameter
values. Take note that plugins have more items in their toolbar and the
new items comes before the usual one, they are : the list of available presets
for the plugin, a rename preset dialog and load and save presets.
Parameter Properties Dialog
In this dialog, you can set the minimum and maximum value to be used for a
parameter, if you want to lock the parameter, meaning that the parameter value
shouldn't change on randomize and mutate, as well as the mutation factor.
In this dialog, you have the list of unlocked and locked for randomize/mutate
parameters and you can quickly change their state by double-clicking on the
parameter name.