Make Canon R40 "Start" button launch NAPS2.

Canon R40 scanner (brand new).
Canon TWAIN driver 1.3.12410.1001, no other Canon software.
Windows 10 Pro 19045.5737.
NAPS2 8.2.0.0.

Want to press the scanner's "Start" button and have it launch NAPS2. It is an inconvenience to go to scanner to load originals, then go to keyboard, launch NAPS2, click on NAPS2's "Scan" icon, go back to scanner to retrieve originals.

Scanner works fine from NAPS2 software.

Can't use W10 control panel to add NAPS2 as a handler for any R40 button events. No button events show up. Following another posted suggestion, I added the StiDevice and StiEvent fields to the registry registration of NAPS2. Didn't help. Any attempt to choose a new handler for the blank event field shown in the control panel results in "The attempt to change the registered event handler failed." Next, I noticed that there was a registry entry for the "scan" button on my HP M479 printer but not for my R40 scanner, so I added a similar entry for my R40. Now an attempt to change the registered event handler for the blank event in the control panel generates no error message, but the "Start" button still does not launch NAPS2.

This error report should replace my previous ticket #1294, which can be marked as closed. I don't know how to mark my ticket as closed.