Definitely check your bylaws. But they may allow you some wiggle room. For example, here's the language from one of my old PTO's:
The Executive Board shall consist of the elected officers, the Past President, the Principal of the school (or a representative appointed by the principal), the Vice-Principal of the school, two representatives elected from and by the school’s professional staff, and the chairpersons of the standing committees. The Executive Board may appoint additional positions as needed.
In our group, we were aware there were sometimes positions added that we wanted included on the Board and we didn't want to be changing our bylaws every year. For instance, when we created ad hoc committees, we'd vote to add that chair to the Board.
"Standing committees" are the ones defined in your bylaws that you always need year after year (Fundraising, Spring Fling, Volunteer, whatever your repeating committees are.) "Ad Hoc" committees are those you create on the fly as needed for how long needed. Maybe they become a tradition and eventually a standing committee, maybe not.
A good example is that PTO didn't normally help with Science Fair, so it wasn't a standing committee. But about every 3 or 4 years a parent would come along that would volunteer to play a bigger role, so that year we'd have a Science Fair Chair (and committee).
In our case, our Board was large (20-30), so adding another position wasn't an issue as long as it was needed. If you have a small Board, like just the 4-5 officers, then adding another position can change the power structure. That's not necessarily bad, but could have more impact.
If you need to change your bylaws, unless you are absolutely convinced this position will last long term, I'd be more inclined to change the language that simply allows you to add more ad hoc members (subject the right conditions/voiting requirement.) That will give you more flexibility.
