Hidden tradeline doesn’t show up on your credit report. Doesn’t affect AAOA or AOYA (clean scorecards for that one anyway), if you carry a balance on it, doesn’t count for revolving utilization etc ad naseum... doesn’t report doesn’t count for anything.
Does reset your gardening date if you are tracking such things (rules are rules), beyond that nothing. No positive benefit either to credit but admittedly many people here have so many trade lines that doesn’t matter in the slightest.