I dont think you would need to change #Main.msg.SelFiles1#
for #Main.msg.Rtsffp# you would get rid of the {0} from "Remove the {0} from playlist '{1}'?" and construct the sentence based on "Remove the selected file from playlist '{1}'?"
I think I don't understand the 'get rid of' part?
For singular, {0} would need to turn out as 'geselecteerde bestan
d'
for plural, {0} would need to turn out as 'geselecteerde bestan
den'
So for both 'geselecteer
de' would be appropriate.
But currently I believe that word is retrieved from #Main.msg.SelFiles1#, where it currently says 'geselecteer
d'.
Which is correct for e.g. "One selected file". But not for "The selected file". (which is what it would ideally be for the entry we are discussing here)
But, the issue got a lot smaller with the new element. I can now get close to 'probably nobody is gonna notice it's not perfect' by just leaving out the word 'The' at the beginning. ('Remove' will be at the end of the sentence in Dutch)