Multiple invoices with ML Extractor

I’m working with different invoices and I’m not doing classification because I know that everytime it will only get invoices. The thing is I don’t want validation station to get open everytime and also want to train the bot. How can I do this?
I cannot use Machine Learning Extractor Trainer because I don’t know how to build custom activity for that.
Can anyone please help me with that?

@Maryum_Siddique you can remove validation station as it is optional.
Putting the classification station is recommended even if want to extract only 1 type of document.
You can create taxonomy for the invoice , follow it up with an intelligent form extractor for a single invoice format.

@Maryum_Siddique you can train the intelligent form extractor for as many invoice formats as you want.