I noticed, that an artist can perform multiple time on the same (festival) event and even on the same day.

It would be nice to add it as credited on the festival page.

Example: Website of Rock in Rautheim with
Sascha Paeth’s Masters of Ceremony and
Sascha Paeth’s Masters of Ceremony - plays Heavens Gate plus special guest

As a workaround, i used the credited as field to enter both appearances:
MusicBraint event

Another example: MPS Bückeburg 1 (scroll down to "Spielplan Markt MPS")
Here for example "The Dolmen" and some other artists are performing multiple times on the same day.