Touch ID becomes an annoyance, when using a MacBook in clamshell mode

For instance: It's a very cool feature, to store an auth token, which allows decryption of passcode-encrypted iWorks docs, via Touch ID.

Except if you've switched to using your MacBook in clamshell mode (i.e.: using an external display, with the lid closed) - in which case, the apps will prompt for the decryption passcode (which, optimally, would be different for each doc) -- even though, in the days before Touch ID, it would store a token accessible via KeyChain.

So, to make the switch back, to using KeyChain instead of Touch ID:

Delete all fingerprints from the Touch ID preference pane, in System Preferences. (Which, since you've switched to clamshell mode, you're rarely using anyway - if ever.)

In retrospect, kinda obvious - though this annoyance has been on my To Do list for awhile. Hopefully this tip saves someone else some trouble.