Dear community

Is it possible to send a test person a second follow-up exactly 4 weeks after completing the first questionnaire?
Limesurvey is still relatively new to me, so any help would be appreciated!

Thank you in advance!

This is not built-in.
You may do it by yourself.
Create a small script (php, or other) to query the LimeSurvey database (via API or directly) to get the "four-weeks-participants".
With something like "phpmailer" send the emails.

This script you call by a cron job each night..
There are a lot of providers of free cron jobs.

Joffm

the task is fairly easy if you know LimeSurveys plugin system:
www.limesurvey.org/manual/Plugin_events

use afterSurveyComplete to create a new token
use direct to invite the participant