instead of _ which results, for example, in "CARWatch_1", I'd recommend adding leading zeroes to the participant IDs (e.g., "CARWatch_001"). The number of leading zeroes should be chosen according to the total number of participants (1-99 => 2 digits, 100 - 999 => 3 digits) etc.
Maybe also check if the layout if adding leading zeroes would break things (also together with #2 )? otherwise, the participant IDs could also be in a separate line, between study name and saliva_id
instead of_ which results, for example, in "CARWatch_1", I'd recommend adding leading zeroes to the participant IDs (e.g., "CARWatch_001"). The number of leading zeroes should be chosen according to the total number of participants (1-99 => 2 digits, 100 - 999 => 3 digits) etc.
Maybe also check if the layout if adding leading zeroes would break things (also together with #2 )? otherwise, the participant IDs could also be in a separate line, between study name and saliva_id