I have used two things:
1)a spreadsheet (date on top of column and symptoms+triggers down the rows) - worked once I got into the habit. In my fog, I often used text/descriptions, but I recommend using a number scale. It helped to group symptoms by type
Physical-motor{fatigue/ataxia/tremor/fascilations/etc}/pain {headackes/soar throat/flulike symtoms/swollen lymph nodes/tender lymph nodes/joint/nerve/muscle} /autonomic {OI/temp instability/palpatations} /gastrourinary {constipation/weak urine stream/urinary urgency} /sensory {sensitivity/visual disturbances/reduced sensation/paresthesia/etc}, sleep {time restful/time restless/quality/cycle shift} , cognitive-mental fatigue/concentration/word retreival/slow thinking/memory recall/memory storage/etc, emotional-stress/agitation/etc, environmental triggers-foods/smoke/mold/temperature, Activity (steps, activity time, , Comments)
This has been my preferred (may be my love of spreadsheets...) but gives me the most flexibility and I find it easiest to scan as I have had various clusters of symptoms come and subside over time, so visually, it has worked the best for me.
2) HealClick (aka MyPatientMatch). You can track as many or as few symptoms as you want on a 1-5 scale if I recall and export to a spreadsheet or it will graph. You can also track treatments (y/n) and the system will (used to) email you daily reminders that it is time to track.