With mate. Is there a setting for it? I don’t understand how this feature is not available it seems so basic.
Is there an entry in the Startup Applications? if so, deselect it and reboot.
Perhaps you mean control over sticky notes at startup? Take a look at System, Preferences, Personal, Startup Applications. Therein, you should find a startup application like Indicator Stickynotes. Make sure it’s checked to run at startup or unchecked to not run at startup.
It’s not there.
But I solved a dropbox indicator icon bug by not starting some indicators. But no sticky notes is not there.