[meta issue] Additional quasi-experimental procedures tracker

Synthetic control extensions

• Augmented synthetic control: https://github.com/pymc-labs/CausalPy/issues/365
• Synthetic difference-in-differences: https://github.com/pymc-labs/CausalPy/issues/47)

DiD extensions

• Event studies https://github.com/pymc-labs/CausalPy/pull/584
• Staggered interventions: https://github.com/pymc-labs/CausalPy/pull/621
• Difference-in-Differences-in-Differences (DDD): #704
• Staggered Difference-in-Differences-in-Differences (DDD): #705
• Hierarchical DiD: #656

RD/RK variants

• Donut RD: https://github.com/pymc-labs/CausalPy/issues/609 , https://github.com/pymc-labs/CausalPy/pull/610
• Fuzzy RD: Issue](https://github.com/pymc-labs/CausalPy/issues/221
• Difference-in-discontinuities [Paper 1, Paper 2]

ITS variants

• Comparative ITS: https://github.com/pymc-labs/CausalPy/pull/595)
• Transfer function ITS: https://github.com/pymc-labs/CausalPy/pull/548)
• PiecewiseITS: [Paper 1, Paper 2, Paper 3, Paper 4] #613, https://github.com/pymc-labs/CausalPy/pull/614
• Changepoint ITS: https://github.com/pymc-labs/CausalPy/issues/767

Panel regression

• Add a new PanelRegression experiment class. It will consume existing linear models. https://github.com/pymc-labs/CausalPy/pull/628

No implementation files, tests, or entry points are named. Start by reviewing the unchecked issues and pull requests for the listed synthetic-control, DiD, RD/RK, ITS, and panel-regression procedures; done means the tracker accurately reflects which procedures are implemented or still have active follow-up work.