After much thinking and no time to test the polyfuse solution, I opted to bypass the burned R1235 resistor in my FT817 with ... another resistor.
I picked an axial 16 ohm 1/4W which was at hand and soldered it in parallel to the original resistor. One lead goes directly to the MiniDin8 socket (PCB solderside). The other lead is held with an ugly blob of solder at the junction of R1235 with the bypass capacitor. I used heatshrink pipe to insulate resistor leads.
One remark about re-assembling the FT817. If you need to move/remove the bottom side PCB, the job is much easier if you remove also the top cover. That's because the mask around the microphone socket is then free to move.
No pictures taken this time.
I might get back inside the 817 and do a proper replacement, but now I am able again to continue the development of my Interactive Frequency Reader with Knob (that's display, keypad and knob all in one!).