An Expert 10×10 Puzzle Solved with Forced Chain in 23 Steps

This 10×10 board rates as expert (difficulty score 1131). Solving it from scratch takes 23 logical steps, using 8 techniques: Single cell, Row/column exclusion, Adjacency clear, Region confinement, Line confinement, Paired regions, Shape squeeze, Forced chain. Every step below is forced: nothing here is a guess.

1. First, every open cell left in this region sits in row 1, so its marker has to land there; that clears every other open cell in the row.
2. Next, every open cell left in this region sits in column H, so its marker has to land there; that clears every other open cell in the column.
3. Then, place a marker at J2. Region has exactly one open cell left. Placing here clears the rest of row 2, column J, and its region. Placing here also clears its 1 touching neighbour.
4. After that, every open cell left in this region sits in column I, so its marker has to land there; that clears every other open cell in the column.
5. Now, together, two regions have open cells only in rows 3 and 4; with one marker each, those two markers have to fill exactly those two rows, so every other region's open cells there can be cleared.
6. From there, place a marker at B5. Region has exactly one open cell left. Placing here clears the rest of row 5, column B, and its region. Placing here also clears its 3 touching neighbours.
7. Following that, every open cell in column A belongs to the same region, so that region's marker has to be somewhere in this column; that clears every other open cell in the region.
8. First, every remaining candidate in this region touches F6 and F7, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
9. Next, every remaining candidate in this region touches G8 and I8 and G9 and I9, so whichever candidate ends up marked will clear them, and they can be ruled out now regardless of which one wins.
10. Then, if E1 were the marker, it would force G4 (the last open cell in row 4), and region 6 would end up with no open cell for its marker, which can't happen. So it can't go there.
11. After that, that one can't be the marker: at F1 it would force G6, G7 and G10 cleared (every open cell left in this region sits in column G, so its marker has to land there), then E6 (the last open cell in region 6), then I10 (the last open cell in region 9), and region 8 would be left with no open cell for its marker.
12. Now, marking G1 would force F3 (the last open cell in region 5), and then row 4 would be left with no open cell for its marker. So G1 can't be the marker there.
13. From there, place a marker at D1. Region has exactly one open cell left. Placing here clears the rest of row 1, column D, and its region.
14. Following that, that one can't be the marker: at E3 it would force G4 (the last open cell in region 5), and region 6 would be left with no open cell for its marker.
15. First, marking F3 would immediately leave row 4 with no open cell for its marker, so it can't be the marker there.
16. Next, every open cell left in this region sits in column G, so its marker has to land there; that clears every other open cell in the column.
17. Then, place a marker at E6. Region has exactly one open cell left. Placing here clears the rest of row 6, column E, and its region.
18. After that, place a marker at C3. Region has exactly one open cell left. Placing here clears the rest of row 3, column C, and its region.
19. Now, place a marker at G4. Region has exactly one open cell left.
20. From there, place a marker at I10. Region has exactly one open cell left. Placing here clears the rest of row 10, column I, and its region. Placing here also clears its 1 touching neighbour.
21. Following that, place a marker at H8. Region has exactly one open cell left. Placing here clears the rest of row 8, column H, and its region.
22. First, place a marker at F9. Region has exactly one open cell left. Placing here clears the rest of row 9, column F, and its region.
23. Finally, place a marker at A7. Region has exactly one open cell left.

The key move here was Forced chain. Once you can spot that, this board falls quickly. ∎