My list is finally ready. All information about the types has been taken from British Secret Projects 1 and British Secret Projects 2, both of which were written by Tony Buttler. Looking thoroughly through these projects was certainly interesting, and makes clear the long line of Scimitar predecessors and derivatives. This list has been separated between Fighters and Bombers (although the line between certain types does get a bit vague).
Fighters:
Type 505: Prepared for the Royal Navy (later made available to the RAF). Emphasis was placed on high rate of climb, so Supermarine designed the lightest possible airframe with the with the largest engine possible (the AJ.65) to provide as much power as possible. The wing was straight and made as thin as possible. This was possible due the the aircraft being designed without a landing gear., instead, a catapult would be needed for takeoff and landing required a mat, something which was being proposed for use on aircraft carriers in the late 1940s. The company also investigated the possibility of making a mixed-power single-engine and rocket aircraft, however, this would require a swept wing, and Supermarine stated that they would not develop this variant until sufficient amounts of information was available on these new technologies. Armament options included the 30mm ADEN cannon, a 4.5in (114mm) recoilless gun, or a 5.9in (150mm) rocket launcher. Although it was never developed, it was the first step towards the Scimitar.
Type 508: Straight wing V-tail prototype. Although it never entered production, it did lay the ground work for what became the Scimitar.
Type 508 F.43/46: A 508 powered by two AJ.65s, carrying four ADEN cannons (alternative armament being a 114mm recoilless rifle). Swept-wing variants also proposed.
Type 511: A thorough proposal for an RAF two-seat night-fighter in two forms; a straight-wing and a swept-wing.
Type 525: Swept-wing prototype, originally designed with a V-tail, later changed to a conventional layout. Set in stone the design of the Scimitar.
Type 526: De-navalised interceptor variant of the 525, with a smaller wing area and a V-tail.
Type 529: Second 508 prototype, fitted with four 30mm ADEN cannons and slightly larger tail.
Type 555: Scimitar prototype fitted with a form of lift-augmentation.
Type 556: Two-seat all-weather fighter, capable of carrying two Red Deans or four Blue Jays and/or cannons. Prototype ordered, but never built, due to the Sea Vixen's entry into service.
Type 558: Scimitar Mk.2 with uprated Avon RA.24s. Main weapon: Firestreak.
Type 560: De-navalised Scimitar.
Type 562: Designed for the interceptor and strike role, capable of carrying Sparrow II AAMs, along with bombs (including Nuclear ordanance) and Blue Jays. Two wing designs were proposed; one with a small aspect ratio and a large area, the other being one with reduced sweep and area.
Type 563: De-navalised Scimitar proposed to a Swiss requirement, not chosen for service.
Type 567 & 574: Scimitar developments.
Type 576: Supersonic fighter based off of Scimitar, originally designed as a strike aircraft. Provision for Firestreaks and Red Tops, along with air-to-air rockets.
Type 588: Studies to fit variable-geometry wings onto the Scimitar, as well as the Swift and the Lightning.
Bombers:
Type 522: Single-seat naval-strike aircraft based off of the 508
Type 537: Strike-version of the 525
Type 561: Low-level nuclear bomber based off of the Scimitar
Type 562: Interceptor and Strike variants off the Scimitar
Type 564: Revised Type 562 for naval use
Type 565: De-navalised, tactical bomber variant of the Scimitar, designed as a Canberra replacement.
Type 567: Single-seat and two-seat strike aircraft for the Fleet Air Arm
Type 572: De-navalised tactical reconnaissance variant of the Scimitar for use with the RAF.
Type 574: Scimitar development.
Trainers:
Type 539: Trainer; seating in a tandem arrangement.