We need to deprecate Custom Variables in favor of Custom Dimensions.
In Piwik 4, maybe we could deactivate the CustomVariables plugin, if no Custom Variable has been tracked so far in this Piwik?
Additionally we would need to find ways to promote the Custom Dimensions feature within the product. By showing some ads or notifications in some way.
Sounds good. I reckon in general it will be a hard transition to get rid of it in terms of providing a good experience to users who still use it. We could for sure mention it in Custom Variables report etc.
Also what about custom variables in scope event?
@tsteur AFAIK the same benefits can be achieved with custom dimensions on events?
Before we can disable custom variables in core, we need to change any core features which currently use Custom Variables (all of it is "hacky"):