Some parameters can be defined has statics : they will not accept changes over the time.
Once Static Parameters are toggled to no static (ie ValueNode , like any other parameters in Synfig) they can be animated, so that they change over time. This can be confusing, make sure you aren't in Animate Edit Mode toggling from "Static" to no static parameter, unless you know what you're doing!
- Static parameter representation in parameter panel
- Change static to no static (right click over param panel)
- ex: Time Loop Layer parameter static by design