Move "Featuring" from Artist to Title

Uhm...how do I add a filter as an action? Or am I understanding this wrong?

There is no action to activate a filter.
If you apply a filter first, you can see if it is necessary at all to start the switching action.
If there are no hits, don't do it.
And if there are, then the action is only applied to the filtered ones which should speed up processing.

Just a footnote: I think that discogs currently always adds the featured artist to the artist field and not to the title field (any more). So maybe you don't have to do it at all, if you want to keep the data that comes from discogs.

Ok, let's see if I got this right. So you mean, run that action group but without the last line on the whole enchilada - because we need to create and populate the feat_artist field, right? - then filter the result by %feat_artist% PRESENT and apply the last step of the action group only on those?

Tried it and it works. Just wondering if there isn't an easier way to do this without splitting the action group/manual intervention....

You could apply the filter before you start the action group. It's a different filter, though:
%artist% MATCHES (featuring|feat.|ft.)

Goodie, that works just fine. 2 things,

I cant save/name a filter string, right?

And is there a way in the replace action to tell it capitalisation doesn't matter? e.g. it picks feat. and Feat. or do I have to do actions for each? I didn't tick the "case sensitive comparison" but the action ignores Feat. and (Feat.)

Yes and no.
The filter string is saved in the dropdown list of the filter.
You cannot save it with a name like the actions or exports.
If you need the filter and some kind of description, so far the advice has been to copy the string to a plain text file and add the comments there. From there, you can copy it back to the filter box.
Can't tell what went wrong with the replace action. It should have worked.

It’s all good. I added another action for Feat. and in combination with the feat. action it works just fine.

Hello

I need some help please. I want to change this thing:

Artist: Cardi B feat. Bad Bunny feat. J Balvin

To

Artist: Cardi B feat. Bad Bunny & J Balvin

Any regular expression to do this in the Artist ? I want only to keep the first "feat." and the others "feat." replace with "&" . There can be more than 2 "feat." in some songs.

Just for the record:
The correct syntax would be "Cardi B, Bad Bunny & J Balvin" (on the album Invasion of Privacy)
There is no explicitly featured Artist for the Song "I Like it", unlike other Songs as "Best Life" or "Ring"

Of course you can change it to whatever you want.

This is not working for me. Here's the original values:

Artist: R. Kelly feat. Game
Title: Playa's Only

The result I'm getting is:

Artist: yame
Title: Playa's Only R. Kell(feat. G)

What am I doing wrong?

You show us the result but not the action and expression with which you got it.
Could you please show us those details as well?

Here is the Action I used:

Action: Guess Values
Source Format: %title% $regexp(%artist%,(. ) feat. (. ),'('feat. $2')' +++ $1)
Guessing Pattern: %title% +++ %artist%

Original Values:
Artist: R. Kelly feat. Game
Title: Playa's Only

Result:
Artist: yame
Title: Playa's Only R. Kell(feat. G)

Intended Result:
Artist: R. Kelly
Title: Playa's Only feat. Game

What am I doing wrong?

The Source is not quite right, try:
%title% $regexp(%artist%,(.*) feat. (.*),feat. $2 +++ $1)

Thank you so much for your help! This worked!