Table Viewer Field hover 'Wildcards' entry meaning

This tag appears if you have a field containing a wild card. For instance, if you use the following script

// ================
Star is *;

AB:
Load * Inline
[A, B
a1, b1
all, *];

BC:
Load * Inline
[B, C
b1, c1
b2, c2];
// ================

This will result in the field B getting the Wildcards tag in the Table Viewer when hovering a field in one of the tables.

This is a very old feature, introduced in QlikView version 1, when it was not possible to handle NULL values and missing values well. Wildcards were used in the data to be able to handle missing values.