What is the constant of blank?

What is the constant of blank? For using in Action Replace.

for exsample
%GENRE%
original: null or empty field (constant of blank used here)
replace to: Pop

As there are no empty fields - if data is not set for a field then it does not exist - use an action of the type "Format value" (in this case for GENRE) to fill a field with data.

OK, get it, :heart_eyes: many thanks :smile: :slightly_smiling_face:

If you want to reuse existing genres and only add Pop for empty/non-existing genres, you can use

$if2(%genre%,Pop)

as format string — or use the Filter before applying the action.