Welcome
Yes, it can be done and I find it very helpful. The problem is that the filter rule only works in the flat People view and not in the Grouped People view so has not been made an automatic installed third party addon.
You can find the code here (and other discussion about it).
Take the two files (activepersonrule.gpr.py, and activepersonrule.py) and place them in your user plugin directory. Your user directory will have a version directory and plugin subfolder (\gramps51\plugins). If you have a folder FilerRules you can put the files there or create the folder.
To actually use the filter, after restarting Gramps, create a filter rule with just this new filter rule in it. Then from the filter you actually want to reference the active person, instead of the rule based upon a static person, set the filter to reference this new active person filter rule. ie Ancestors of <filter> match