It only took me ONE failed marriage to figure out "that dog don't hunt".

You're gonna hafta figure out some way of siphoning off a few bucks per paycheck and stuff it into an account that the little woman has no knowledge of.

Aside from having some scratch to hobby with I implore you to set up one or more clandestine accounts that the misses has no knowledge of or access too.
This is the new millennium; you don't go into marriage blind, dumb, and idealistic like Paul McCartney did with Heather Mills.

I don't have that issue, since we have separate accounts, but still, I make sure that I buy lots of stuff for work and cash the expense report check.  Some of it gets into the bank, but I hold back a bit.  The other thing I use is casinos.  If there's one nearby, frequent it, and get known well enough that if your wife is ever with you, someone greets you by name.  Once you're at that point, you can filter off some cash explained away as gambling losses.  The trick then is to not gamble it away, and not make it so much that she makes you stop gambling.

I took over all of the bill paying and expenses after the SO complained about how much work it is to do this. We have a joint account for many of the expenses.

I have a separate account that my paycheck is auto deposited to.  The SO has no access to this account, until I am deceased.  I pay some bills as needed from this account, but I also set aside some funds from every check to cover my "personal needs."

That's what kept me fueled for many a year until I got caught and ended up in divorce court.

Now I'm free, just a lot lighter in the bank account.

Fortunately, the ex never was into checking the tax forms, where all this would have shown up.

Moral of the story here:  Do not marry an accountant if you plan to hobby.