Write WGSL or GLSL in the Shader editor, or point a shader at a file and keep your own editor open: save, and it recompiles. Errors name your own line, and the last picture that worked keeps drawing while you fix it.
Paste a Shadertoy, set the language to GLSL and tick Shadertoy compat. A comment like // @range(0, 3) above a uniform gives it a slider, and any uniform can follow a song, a MIDI knob or the clock instead of a number. Run up to 64 passes, write up to 7 pictures at once, feed frames back into themselves, or move the points of a mesh in a vertex shader.
Python lives in the same graph: scripts that add and wire nodes, one-line expressions on any setting, and the packages you install with kinematic pip.