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make a log backup before doing any en masse update.
Filter the log for the QSOs you need to modify.
Then open the (ADV)anced dialog.
At bottom select the field to be "bulk" modified in the "Item name"
combo box, in this case QSL_Sent.
Select the new value in the "Item new value" combo box, in this case
nothing (NULL), leave the combo empty.
Click the Mod button to update.
Did I alredy mention to BACKUP THE LOG before doing this operation? :-)
Did I alredy mention to FILTER THE LOG before doing this operation? :-)
I guess that the (R)equested value is a default, but I don't remember if
there is a setting modifiable by the user.