This thread is for collecting links to the available GT6 course maker tools and resources scattered around GTPlanet, to make them easier to find. If you know about a resource that is not listed here, please post the link and I'll add it to the OP. If you don't want your resources listed here, let me know and I'll remove them.
A. Course Creation Tools (for creating new tracks)
i. Track Path Editor
The official app released by PD for iOS and Android.
On Google Play
ii. Alternative APK's (for Android)
Alternative versions of the official app. Earlier versions and modded versions.
1.0.1: No link
@J24681357 's mod (flat tracks).
@PR1VATEJ0KER 's mods (wild elevations / disabled checks & homestraight anywhere / disabled checks).
iii. Android Emulators
For running the Android app on a PC
List of Android emulators
iv. Third Party Course Makers
For creating tracks from scratch
@eran0004 's Track Layout Creator (Python 3.6 or higher required)
B. Course Editing Tools (for editing and modding tracks)
i. TED Extraction and Uploading
For extracting the TED files from GT6 replays and for uploading TED files to GT6.
@Razerman 's GT6Web_WFA extractor and uploader
ii. Hex Editors and resources
For viewing and manual editing of TED files.
010 Editor (Free 30-Day Trial)
@Razerman 's 010 Editor TED template
@Mr Grumpy 's road and decoration codes
@NingDynasty 's 010 Editor TED templates (including road and decoration codes)
iii. TED Editors
For editing of TED files.
@tarnheld 's TED Editor (Python 3 required)
@eran0004 's Elevation Editor v.1.1.5 (Python 3 required)
C. Other resources
Polyphony Digital's Track Path Editor Manual
ii. APK Height Maps
For viewing the elevation of the course maker sceneries.
@Outspacer 's .raw height maps.
@Outspacer 's contour maps (Andalusia, Death Valley, Eifel, Eifel flat)
@eran0004 's contour maps: Andalusia, Eifel
iii. Track Reference Data
@Silvio 's Satellite Track Maps
@Sploshington 's Classic GT Track Layouts
Geocontext Profiler (for generating real world elevation profiles)
Maps to GPX
iv. Course Sharing
GTPlanet's GT6 Track Database