Update all Titles without filtering

I'm sure this is very simple, but I am new mp3tag user, and I can't find the answer in docs, faqs, or by searching (hard to search for).

I have a list of mp3 files (audiobook) that I dropped in mp3tag (v2.82). They're all in the right order (sorted by filename). I want to set the Title to something (with a counter), regardless of what it is right now. So I created an action, with the following properties:

Field: TITLE

Original: (I don't know)

Replace with: Example L$num(%counter, 2)

(In this example, I would like the titles to be "Example L01", "Example L02", etc.

I tried leaving original blank, but pressing the ok button on the action edit dialog doesn't work. I tried using *, I tried using %1 %2, "%1 %2" (the current tile is Lecture 01, Lecture 02, etc). Every time I run the action the result is "formatted tags in 0 out of 18 files".

I assume that my replace with expression is fine, but my 'original' is not. What do I need to enter in 'Original' so that it doesn't filter - just ignores whatever there is? And why doesn't %1 %2 work? Or is there an easier way to accomplish this than a replace

You can only replace something that is already there.
An empty field actually does not exist in a tag.
The correct action would be:
Format value for TITLE
Format string: Example L$num(%_counter%, 2)

Or use the function Convert>Tag-Tag
with the same parameters. That function has also a preview.

Ah yes, Convert >Tag-Tag worked immediately, thanks!