This is not meant to be a technical response to what can and can’t be done in the apps, but rather a pedagogical one.
Mnemonics are techniques used to make it easier to remember something, which can happen in various ways. If you don’t remember the mnemonic, it isn’t working and it’s not doing it’s job. Find another mnemonic.
If you remember how to write something after peeking at the mnemonic, that’s basically the same thing as having looked at the answer from a memory retention perspective. The question the writing card asks is “how do you write the character that means this and is pronounced like that?” and the answer to that question is “no” if you have to look anything up, definitely including the mnemonic.
Looking at the mnemonic and then writing answers a completely different question, namely “how do you write the character indicated by this mnemonic?” That’s a very artificial question and I would argue only useful in very limited cases, such as if you used flashcards to cement a peg system of some kind, i.e. if you arbitrarily connect some meaning to certain character components and need to study these connections. That’s not something supported in Skritter, though.
Now, I realise you probably have a good reason for wanting to do this, I’m just outlining that in general and for most people, there’s no real need for being able to look at the mnemonic, write the character and then reveal the full answer. Would you mind expanding a bit on your reasons for wanting to do this?
In my opinion, a mnemonic is not very good if you need to look it up and I would come up with a new one instead. Sometimes, it’s of course necessary to look them up in general to make sure they are consistent across many characters and words, but that’s unrelated to reviewing.