[Help] D&D multiclass error

I got a player that is a Rogue Thief. At level 5 she wanted to changed her class to a arcane trickster. So she is multiclassing. But every time they level up I get a error and have to remake their character sheet from scratch. Any advice or help?  

Thief and Arcane Trickster are both subclasses of Rogue.&nbsp; RAW, this is not supported by multiclassing rules, so it's not surprising that the Charactermancer does not support it. Here is a link to Sage Advice clarifying this:&nbsp; <a href="https://www.sageadvice.eu/can-i-multiclass-into-same-class/" rel="nofollow">https://www.sageadvice.eu/can-i-multiclass-into-same-class/</a> Tasha's Cauldron of Everything does have an optional rule (p.8) that allows you to completely replace your subclass with the features of a different subclass.&nbsp; Not sure how that works with the Charactermancer, as I haven't tried to do that.

Anthony said: Thief and Arcane Trickster are both subclasses of Rogue.&nbsp; RAW, this is not supported by multiclassing rules, so it's not surprising that the Charactermancer does not support it. Here is a link to Sage Advice clarifying this:&nbsp; <a href="https://www.sageadvice.eu/can-i-multiclass-into-same-class/" rel="nofollow">https://www.sageadvice.eu/can-i-multiclass-into-same-class/</a> Tasha's Cauldron of Everything does have an optional rule (p.8) that allows you to completely replace your subclass with the features of a different subclass.&nbsp; Not sure how that works with the Charactermancer, as I haven't tried to do that. That makes sense. Thanks for the reply!&nbsp;