Workspace: Add option to filter search results with only custom variables vs. default variables

There are custom variables (props and eVars, and of course events as well) and then there are out of the box or should I say default variables and metrics. Would be great, if again I could have the option to search just among custom variables or among default variables. Let's say product owner knows we are using some kind of custom variable where we have put e.g. mobile billing information, but he can't remember it was eVar86. He starts to search with word "mobile", but then he sees over 20 default variables with word "mobile" and he can't see the eVar he is looking for without scrolling search results. If he could filter to search only among custom variables then problem solved. Of course he can already search by "mobile eVar", but filtering option for custom variables would be much easier to use and remember.

Of course, even better would be to search by (automatically generated!) tags:
eVar / prop / events / default variables / default metrics

But even the first idea would be a great start!