Some background information:
There are two methods to inhibit an aircraft's track.
1. Open the flight plan window for the aircraft, press the inhibit button in that window, or
2. Select the aircraft's symbol on the screen, press (effectively) Shift-F6.
The results are instantaneous. There are no on screen prompts such as "Confirm Inhibit (callsign)?" (as there are for cancelling an aircraft's flight plan, or removing the flight progress strip).
The aircraft label and symbol will turn black (the "Not Concerned" display state colour), the "cleared flight level"in the label (used as a highlight prompt for the receiving sector) will disappear.
The only feedback the controller has that the aircraft has been inhibited is that the label goes from green to black, which entails watching the selected track change as you are pressing the right buttons on the screen or keyboard. Expectation bias can play a great role here.
The next sector to manage the aircraft, if watching at that exact moment, will see a blue label, with highlighed cleared flight level, go to black with no highlight. The approaching aircraft label will not flash orange on handover, approaching the airspace boundary, and there will not be a system prompt for a frequency transfer.
The ATC's Short Term Conflict Alert still works between inhibited tracks and other controlled tracks.
"Black tracks" (also know as "unconcerned" or "background tracks" in the ATC system, TAAATS) are to assist the controller differentiate between the traffic under (or about to be under) their jurisdiction (green, blue or orange coloured) and other traffic beneath or above the airspace that are being managed by another controller, or VFR aircraft in Class G or E airspace not receiving a service (black).
With no further system prompts the presence of the inhibited aircraft is dependent upon the controllers' scan. The system is biased toward assisting the controller ignore unconcerned aircraft by making their labels black, and if it is airspace that is not normally subjected to unconcerned tracks (eg high level enroute) then that bias is reinforced. There are additional tools to enable differentiation between concerned and unconcerned traffic, such as altitude-based filters, which enable display of an aircraft's symbol (the circle) but not the label (callsign, level etc). This is to minimise "screen clutter".
(As an aside, Australian enroute controllers do not have planner controllers available as a second pair of eyes in normal operations.)
This video is an interesting exercise relevant to the scanning for black tracks issue. How well did you do?
It is linked to as part of the refresher training CBT module for Scanning.
Cheers