Can thrust vectoring be used to enable the use of flaps on tailless delta-winged aircraft?
No, for several reasons

What you want is to compensate for the additional lift from downward deflected flaps at the back of a flying wing with vectored thrust. As @Sean points out this will not bring a noticeable net benefit if the lengthwise location of both forces is similar.

But that is not all.

Besides the force equilibrium around the flying wing you also need to consider how it behaves when flight parameters change, say by gusts. Will it return to the old state? How will the dynamic behavior be?

More camber means that the zero lift angle of attack becomes more negative. A deflected flap adds camber near the trailing edge. If the wing now assumes a higher angle of attack due to a gust, the change in local lift over chord will make the wing pitch up more. The forward region of the airfoil will add more lift relative to the initial state than the rear region because the zero lift angle of attack has been shifted downwards, adding a pitch-up moment. The whole aircraft will become unstable from the added camber of the flap.

Flying wings don't need computer control. All the Hortens and Fauvels of this world flew just fine with a human pilot and mechanical controls. That is because they use reflex airfoils and wing twist so the rear part of the wing creates less lift relative to its area. This is the condition for static stability and it gets removed with a positive flap deflection.

Adding that flap will add so much instability that computer control would have a hard time to keep the aircraft stable. If the flap produces substantial additional lift, the thrust vector control would need to effect large changes in pitching moment. Now consider you fly into an airport along the glide slope, with the engine close to idle. Where would the required pitching moment come from? Thrust is insufficient and reducing your flap setting will stall the aircraft. The best solution is to not deflect the flap in the first place and to add more wing area relative to a conventional aircraft.