I can't see the sub-actions being used, so I can't tell what is being done there. You could do the following:

Force Grouped Execution
Test if the Artist field is not equal to "\[Album Artist]" (Set result)
if true
Append "…-…" and the Album Artist field to the Title field
endif

Please view the above in the forum as the mailer strips out backslashes. The ... sequences are use to represent leading and trailing spaces and/or newline characters.

Yate allows you to insert the current and initial contents of any of its fields directly into most action statements. Rather than remember the exact field names and the cryptic escape sequences you can do the insertion from a field's context menu via Insert Yate Field.

If for some reason, and there are may valid reasons, why you want your main action to run stepwise you can always do the work above in an inline action:

Run inline action 'Compare and Possibly Append' grouped
.
.
.
Start Compare and Possibly Append
Test if the Artist field is not equal to "\[Album Artist]" (Set result)
if true
Append "…-…" and the Album Artist field to the Title field
endif