Here, a user notes
Here’s a list of all the keyboard shortcuts built into Tinderbox, but it’s not very helpful in terms of finding out which keys are available for a custom shortcut.
But there is a list, for just such “what is still free purposes”: Reverse Look-up Map†. It is deliberately organised by key, then modifier. So first there is ‘A’ and we find the following A-based shortcuts are in use:
A+[Cmd]: Select All
A+[Ctrl]: Scroll to top of window (Home)
A+[Cmd]+[Shift]: Create Agent
A+[Cmd]+[Opt]: Attribute Browser view (change current tab’s main view type)
A+[Cmd]+[Opt]+[Ctrl]: Deselect All (hold Opt to see in menu)
Ironically, only just this last weekend I reviewed all the app main menus and their sub-menus and added any relevant shortcuts to the note $Text. I’ve deliberately used the order as show on the menus themselves. Though visibly in the pages’ screengrabs, I figured having the short-cut in the note text makes it easier to copy paste elsewhere for personal reference.
Also there are apps like KeyCue and CheatSheet and likely others that let you hold down a key and see an overlay showing you the frontmost apps current shortcuts.
†. I surprised myself in finding this page has been around since the very early days of aTbRef and is in the oldest baseline (v2.3.4–v4.2.5) version here. At least, it pre-dates v3.5.0 so that page has been supporting the Tinderbox community since at least June 2006—at least 15 years and counting. 