An Expert 10×10 Puzzle Solved with Forced Chain in 31 Steps

This 10×10 board rates as expert (difficulty score 1501). Solving it from scratch takes 31 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, together, two regions have open cells only in rows 1 and 2; 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.
2. Next, that one can't be the marker: at C1 it would force D3, E3, F3, and 8 more cleared (together, two regions have open cells only in rows 3 and 4), then A5, B5, G5, and 3 more cleared (every open cell left in this region sits in row 5, so its marker has to land there), then I2, I3, I4, and 3 more cleared (every open cell left in this region sits in column I, so its marker has to land there), and the chain continues, and region 6 would be left with no open cell for its marker.
3. Then, that one can't be the marker: place it at F1, and row 2 would be left with no open cell for its marker.
4. After that, if H1 were the marker, it would force I8, I9, I10, and 5 more cleared (together, two regions have open cells only in columns I and J), then G9, F2, F3, and 5 more cleared (together, two regions have open cells only in columns G and F), then E2 (the last open cell in region 2), and the chain continues, and column J would end up with no open cell for its marker, which can't happen. So it can't go there.
5. Now, that one can't be the marker: at I1 it would force A3, B3, C3, and 4 more cleared (every open cell left in this region sits in row 3, so its marker has to land there), then B4, B5, B6, and 9 more cleared (every open cell in column A belongs to the same region, so that region's marker has to be somewhere in this column), then B9 (the last open cell in column B), and the chain continues, and row 10 would be left with no open cell for its marker.
6. From there, if F2 were the marker, row 1 would end up with no open cell for its marker, which can't happen. So it can't go there.
7. Following that, if I2 were the marker, region 4 would end up with no open cell for its marker, which can't happen. So it can't go there.
8. First, 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.
9. Next, if A3 were the marker, it would force I4 (the last open cell in region 4), and region 8 would end up with no open cell for its marker, which can't happen. So it can't go there.
10. Then, 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.
11. After that, that one can't be the marker: at B3 it would force I4 (the last open cell in region 4), and region 8 would be left with no open cell for its marker.
12. Now, marking D1 would force G2 (the last open cell in region 3), then B9 (the last open cell in column B), then H6, J6, H7, and 5 more cleared (every open cell in row 8 belongs to the same region, so that region's marker has to be somewhere in this row), and then row 10 would be left with no open cell for its marker. So D1 can't be the marker there.
13. From there, if E1 were the marker, it would force G2 (the last open cell in region 3), then B9 (the last open cell in column B), then H6, J6, H7, and 5 more cleared (every open cell in row 8 belongs to the same region, so that region's marker has to be somewhere in this row), and row 10 would end up with no open cell for its marker, which can't happen. So it can't go there.
14. Following that, marking G1 would force E2 (the last open cell in region 2), then B9 (the last open cell in column B), then H6, J6, H7, and 5 more cleared (every open cell in row 8 belongs to the same region, so that region's marker has to be somewhere in this row), and then row 10 would be left with no open cell for its marker. So G1 can't be the marker there.
15. First, place a marker at G2. Region has exactly one open cell left. Placing here clears the rest of row 2, column G, and its region. Placing here also clears its 2 touching neighbours.
16. Next, place a marker at B1. Region has exactly one open cell left. Placing here clears the rest of row 1, column B, and its region.
17. Then, every remaining candidate in this region touches J4, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
18. After that, marking C3 would force I4 (the last open cell in region 4), and then region 8 would be left with no open cell for its marker. So C3 can't be the marker there.
19. Now, every remaining candidate in this region touches D5, so whichever candidate ends up marked will clear it, and it can be ruled out now regardless of which one wins.
20. From there, if D3 were the marker, it would force I4 (the last open cell in region 4), and region 8 would end up with no open cell for its marker, which can't happen. So it can't go there.
21. Following that, that one can't be the marker: at E3 it would force I4 (the last open cell in region 4), and region 8 would be left with no open cell for its marker.
22. First, every open cell in row 3 belongs to the same region, so that region's marker has to be somewhere in this row; that clears every other open cell in the region.
23. Next, together, two regions have open cells only in rows 4 and 5; 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.
24. Then, place a marker at F6. Region has exactly one open cell left. Placing here clears the rest of row 6, column F, and its region. Placing here also clears its 2 touching neighbours.
25. After that, place a marker at E4. Region has exactly one open cell left. Placing here clears the rest of row 4, column E, and its region.
26. Now, place a marker at C5. Region has exactly one open cell left. Placing here clears the rest of row 5, column C, and its region.
27. From there, place a marker at I7. Region has exactly one open cell left. Placing here clears the rest of row 7, column I, and its region. Placing here also clears its 2 touching neighbours.
28. Following that, place a marker at J3. Region has exactly one open cell left. Placing here clears the rest of row 3, column J, and its region.
29. First, place a marker at D10. Region has exactly one open cell left. Placing here clears the rest of row 10, column D, and its region.
30. Next, place a marker at H9. Region has exactly one open cell left. Placing here clears the rest of row 9, column H, and its region.
31. Finally, place a marker at A8. Region has exactly one open cell left.

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