At one moment I had 8 girlfriends. They all knew they weren't exclusive, some of them knew others, some of them didn't. In fact this was my seduction strategy to tell them I sleep with many girls.
It goes like this:
Her: Do you have a girlfriend? (they always ask, it also shows that she is really interested in you)
Me: No. I dont have A girlfriend. I have eight girlfriends. And actually I am looking for a ninth one. And after talking to you I see you are a very interesting and attractive girl, I like you so much that I can offer you place number 5 right here.
Her: No, I want to be number one.
Me: I cant give you number one, since all 8 of them are going to be offended. I am kinda offending 3 girls already by giving position 5. I suggest you start from there, and if you behave you can work your way to the top.
This is how you do it.
Do you need to hide the fact that you have other girls or as one of my friends did, keep track of what you talked about in an Excel spreadsheet and memorize everything?
No memorizing, no hiding. You dont need to tell them if they are not asking. And if they are smart enough and dont want to know, they wont ask.
Lying is not only unethical, you dont grow like a man when you lie in this particular manner. Alpha male has the right to fuck whoever and whenever he wants. And we all know girls like alpha.
Lying and hiding is not alpha.