I just found this dutch Denksport puzzle book from 2011 in my drawer. I have no clue what this puzzle type is called, I just know that I used to like it and that it's called "Zoekplaatje" in dutch.

@michaln I think it's like Picross (or Nonogram, according to Wikipedia) but there the numbers are shown on the edges of the grid.

Edit: It could also be "Paint by pairs" or "Link-a-Pix" (found on the same Wikipedia page): "Paint by pairs or Link-a-Pix consists of a grid, with numbers filling some squares; pairs of numbers must be located correctly and connected with a line filling a total of squares equal to that number."

(https://en.wikipedia.org/wiki/Nonogram#Other_picture_logic_puzzles)

Nonogram - Wikipedia

@loadhigh the idea of this one is that you connect identical numbers nearby, such that if you're connecting N to N, the path between them should cover N squares (including the numbers). For example, if you connect a 4 to another 4, you should fill in 4 squares.
@michaln That sounds like the description of "Paint by pairs" or "Link-a-Pix" that Wikipedia mentions (https://en.wikipedia.org/wiki/Nonogram#Other_picture_logic_puzzles)
Nonogram - Wikipedia

@loadhigh yes, that's exactly it! thank you 🙏