If we're discussing the radical, it can be written with either 6 or 7 strokes, depending on if the kanji that uses it is a 新字体, like 舞, or if it's a 旧字体 or never got a 新字体 version, like 蕣.
The shape alone isn't that common I don't think. Except in names or place names, maybe? It's a 人名用漢字.
Oh, forgot to say the newer (新字体) versions use 7 strokes and older (旧字体) versions use 6 strokes.
Oh, I wasn't aware of that. I was actually brushing up on radicals when this one came up and I started wondering what else it's being used in.
I just tried looking it up and from what I can see the general consensus is that it has 6 strokes. I personally haven't seen it being written with 7, but I'll take your word for it being a new and old form thing. Still though, the stroke breakdown uses the 6-stroke variant while the actual count is shown to be 7 which I think we can agree is kinda confusing.
Compare the stroke order diagram for 舞 with the stroke order diagram for the radical alone.
The right side element of the radical is 4 strokes there, whereas it's 3 in the old version, making the whole thing 7.
https://jisho.org/search/%E8%88%9E%20%23kanji
This is the most commonly encountered form of the radical, unless you start to study well beyond the jouyou kanji set.
This now shows with both 6 and 7 as possible counts, with 6 being the preferred.
Incorrect stroke count and grouping for 舛
https://jisho.org/search/%E8%88%9B%20%23kanji
As the title says, the stroke count shows up as 7 when it should actually be 6 and it's also grouped with the other 7-stroke radicals in the selector.