Hi @Thijs,
Sorry for getting back to you only now.
As you’ve might’ve noticed, using the period. in an account or reconciliation template will cause the “copy data” function to not work at all.
So never use period.custom in those templates.
to get back to your question :
Is it (with a workaround) possible to copy data to another period with the period.custom drop?
Actually, there is.
You could create a text template where you have your period.custom drop but you’ll add a rollforward to it that will copy data from your period.custom to the new period custom drop.
The rollfoward is explained here:
Hope this helps and I’m not too theoretically - let me know if you are stuck and perhaps I can create a case for this as well