Switching to matrix planner removes lines - should be disabled instead

[Soul-Burn]

Suggestion

If you make a large planner using matrix planner, with by-products and all, clicking to normal removes many lines which don't return when clicking back.

Suggestion: Mark these lines as disabled in some way instead of deleting, so that returning to matrix solver is easy.

Steps to reproduce:

• Switch to matrix solver
• Add a couple of lines, including by-product lines
• Switch to linear solver
• Switch to matrix solver

Expected: Lines remain, and switching to matrix works

Actual: Lines are removed, breaking the plan

[ClaudeMetz]

Yes this is a great suggestion, no idea why I didn't think of it before. Will be a bit more tricky to implement, but no big deal. Thanks a lot.