Automation Toolkit Free lets you create your own custom buttons with their own functionality inside After Effects. Alon Shemer describes it as a "Whatever You Want!" button maker, and the action library is broad: layer properties such as position, rotation and time remapping, composition and project actions, render queue and output module settings, plus file and folder operations.
Beyond the built-in actions, it can run JavaScript code with variable inputs and code results, work with CSV data from Google Sheets or Excel, and handle keyframe tasks like retiming, offsetting and copying keys. You can precompose, add solids, nulls, cameras, lights and shape layers, apply animation presets, send comps to the render queue or Adobe Media Encoder, and apply render templates.
Some things are out of scope: shapes and masks can't be accessed, text layers support only source text, font, font size and justification, and certain keyframe properties such as interpolation and hold can't be changed, though keyframe values can. It ranks 58 on aescripts and runs on After Effects 2023 back through CC 2018.