Hi,
Yea, Having no timestamp at all, because you forgot to switch it on - I can feel the pain 
As some users wrote in the related thread, they even switch of created, because for a lot of tiddlers it can reduce wiki size.
The usecase you describe is completely different and “domain specific” as so often with TW.
I can see the desire, to date back the modified field to get a tiddler “back into context” in the timeline. For teachers that makes sense, if users remember: “Ahh we did that 2 months ago”, but the tiddler is in the Recent tab 1 week ago, because it needed some typo fixing and Timestamp On was active 
I think it would be needed that
- If Timestamp is off
- The Tool button needs to be forced to be visible
- There may be 2 buttons
- One for
createdfield update on/off - One for
modifiedfield update on/off
- One for
- Hidden settings:
- Do not create created date
- Do not create modified date (IMO only for consistency)
- New dialogue
- List of checkboxes with field names
- Button delete them
IMO related and long standing:
- Import should update modified and create created field
- Make it configurable in a similar way as above
I think that would cover all usecases. So IMO it will actually be more work as it first seemed, if it is done consistently. I’m not sure if Jeremy will like that extra complexity. So may be a plugin.
Just brainstorming, no promises.