For running J!5.1 you must https://fabrikar.com/forums/index.php?wiki/update-from-github/ or include the new file manually https://fabrikar.com/forums/index.php?threads/joomla-5-1-and-fabrik-cannot-find-files-error.54473/post-285151 See also Announcements
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I've the following aswer :Wiki? http://fabrikar.com/forums/index.php?wiki/groups/#repeatable ?
Please use the other forum if you're not using Joomla 2.5 and Fabrik 3.0, thanks.
In the 'add' form, I don't find the setup to add several records in one time adding a '+' icon.
You can use the repeat group feature @lousyfool mentioned to "fake" something like a multi-record add but in this case you need a dummy list and join it with "repeatable" to your list you want to add the records to (so you'll need an adddtional FK/parent_id element in your list)